Disposable food contact compatible microwaveable containers having at least one micronodular surface and process for their manufacture

ABSTRACT

Disposable food contact compatible microwaveable containers having one or more micronodular surface are disclosed. These containers, including plates, bowls, cups, trays, buckets, souffle dishes, and lids are prepared from a polyolefin selected from the group consisting of polypropylene, polypropylene polyethylene copolymer or blends, and mixtures of these, mica, and pigment and are thermoformed into the shape of a the aforementioned containers exhibiting (a) a micronodular surface on at least one side of the surface; (b) a melting point of not less than about 250° F.; said containers being dimensionally stable and resistant to grease, sugar, and water at temperatures up to at least 250° F. and being of sufficient toughness to resist cutting by serrated polystyrene flatware.

RELATED APPLICATIONS

This application is a continuation in part application of Ser. No.08/733,463 filed on Oct. 18, 1996, now abandoned.

BACKGROUND OF THE INVENTION

This invention relates to disposable food contact compatiblemicrowaveable containers having at least one micronodular surfaceincluding cups, trays, souffle dishes, lids, plates, bowls, and relatedarticles of manufacture useful for preparation, storage, delivery, andserving of food, wherein convenience and low cost are of paramountimportance. Nevertheless, appearance and tactile characteristics of theplate, container, etc., are important for consumer preference. Thesuitability of these disposable articles of manufacture for microwavecooking, or heating of food, has an important place in today'smarketplace. Both the commercial and retail market components need anaesthetically pleasing microwaveable, disposable, rigid and strongcontainer, plate, or cup, and related article of manufacture. Thisinvention is directed to economically meeting that need and provides acontainer or plate comprising an extruded sheet of a polyolefin selectedfrom the group consisting of polypropylene, polypropylene polyethylenecopolymer or blend, or a mixture of these coupled with mica or a similarplaty inorganic mineral.

These disposable microwaveable containers and plates exhibit (a) amicronodular surface on the food contact side of the plate or container,and (b) a melting point of no less than about 250° F., said container orplate being dimensionally stable and resistant to grease, sugar, andwater at temperatures up to at least 220° F. and exhibiting sufficienttoughness to be resistant to cutting by serrated polystyrene flatware.Microwaveable and disposable containers and plates having all theaforementioned properties are not known in the prior art. In U.S. Pat.No. 5,377,860, assigned to assignee of the present patent application, adouble shell food container is disclosed. The composition and propertiesof the container differ from the present invention since apolyolefin/mica composition is not suggested or disclosed and thecontainer does not have the thermal properties or the micronodularsurface of the containers disclosed herein. The containers disclosed inEuropean Patent Application D544,429A1 do not suggest or disclose acontainer which can meet the thermal properties and have the desirablemicronodular surface of the container of the present invention.

SUMMARY OF THE INVENTION

Microwaveable, disposable, rigid, strong and food contact compatiblecontainers and plates have been prepared. These disposable andmicrowaveable articles of manufacture exhibit (a) a micronodular surfaceon the side coming in contact with the food; and (b) a melting point ofnot less than 250° F., suitably 250° F. to 330° F. These microwaveable,food contact compatible containers and plates are dimensionally stableand resistant to grease, sugar, and water at temperatures of at least220° F. and are of sufficient toughness to be resistant to cutting byserrated polystyrene flatware. These containers, in the form ofdisposable lunch (8.75 inch) and dinner plates (10.25 inch), exhibit aSSI rigidity of at least 200 grams per 0.5 inch at a basis weight ofabout 130 lbs. per 3000 square foot ream. At a basis weight of about200, SSI rigidity is about 300 grams per 0.5 inches; and at a basisweight of about 360, SSI rigidity is about 700 grams. The containers andplates of this invention answer a long felt need for products which canwithstand the severe conditions of a microwave oven when common foodssuch as beans and pork, pancakes with syrup, pepperoni pizza, andbroccoli with cheese are microwaved during food cooking andreconstituting processes. When the polyolefin is combined with mica,these containers and plates exhibit a micronodular surface on one orboth sides usually on the side coming in contact with the food.

As shown in Example 9 and Table 12, competing commercial polystyrenetype plates cannot withstand the high temperatures generated in themicrowave oven during food contact and either significantly warped ordeformed when the aforementioned food products were placed on them.Under the usual microwaving conditions with high grease content foods,the prior art plates tend to deform and flow to the point where parts ofthe plate became adhered to the inside of the microwave oven. Fordisposable plates and containers, appearance and feel are importantattributes. The micronodular surface of the plates and containers ofthis invention where mica is used in combination with polypropylene orpolypropylene polyethylene copolymers or blends tend to give theseproducts the pleasing appearance and feel of stoneware or a pottery-likelook. Another significant property of the containers and plates of thisinvention is their cut resistance. These rigid articles of manufactureare of sufficient toughness to be resistant to cutting by serratedpolystyrene flatware. In normal usage they are also resistant to cuttingby regular metal flatware.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given herein below and the accompanying drawings,which are given by way of illustration only, and thus, are notlimitative of the present invention and wherein:

FIG. 1 is a schematic flow diagram of the sheet extrusion process.

FIG. 2 is a schematic flow diagram of the thermoforming process for themanufacture of plates and containers having the micronodular surface.

FIG. 3 is a graph comparing the rigidity of the plates of this inventionwith prior art commercial products in the context of current materialcosts.

FIG. 4 is a bar graph comparing the heat resistance of the plates ofthis invention with prior art commercial products.

FIG. 5 is a drawing of a plate of this invention.

FIG. 6 is a cross sectional view of the plate shown in FIG. 5.

FIG. 7 is a radial cross-section of the plate shown in FIG. 5.

FIG. 8 is a schematic profile of the plate shown in FIG. 5, beginningfrom the center line of the plate, formed in accordance with the presentinvention.

FIG. 9 is a drawing of a plate of this invention.

FIG. 10 is a cross sectional view of the plate shown in FIG. 9

FIG. 11 is a radical cross section of the plate shown in FIG. 9.

FIG. 12 is a schematic profile of the plate shown in FIG. 9 beginningfrom the center line.

FIG. 13 is a drawing of a tray included in this invention.

FIG. 14 is a cross sectional view of the tray shown in FIG. 13.

FIG. 15 is a radical cross section of the tray shown in FIG. 13.

FIG. 16 is a schematic profile of the tray shown in FIG. 13 beginningfrom the center line.

FIG. 17 is a drawing of a bowl of this invention.

FIG. 18 is a cross-sectional view of the bowl shown in FIG. 17.

FIG. 19 is a radical cross section of the bowl shown in FIG. 17.

FIG. 20 is a schematic profile of the bowl shown in FIG. 17 beginningfrom the center line.

FIG. 21 is a drawing of a take-out food container included in thisinvention.

FIG. 22 is a scanning electron photomicrograph of a plate (upperpicture) and a sheet (lower picture) of this invention showing themicronodular food contact surface of the plate but not so for the neatextruded sheet.

FIG. 23 is a graph plotting gloss versus mica level.

FIG. 24 is a graph plotting the plate rigidity versus mica level.

FIG. 25 is a scanning electron photomicrograph of a sheet of thisinvention showing a matted surface and a nonmatted surface.

FIG. 26 is a scanning electron photomicrograph of a sheet of thisinvention showing two high gloss sides.

DETAILED DESCRIPTION OF THE INVENTION

The aesthetically pleasing microwaveable disposable, rigid and strongcontainers including plates, bowls, cups, trays, buckets, souffle dishesand lids comprise isotactic polypropylene, propylene-ethylene copolymer,or blends of isotactic polypropylene and propylene-ethylene copolymercoupled with a mixture of a platy inorganic mineral such as mica.Suitably coupling agents and pigments are utilized. To form suitablecontainers, bowls, trays and plates having excellent thermal,mechanical, and other physical properties and also exhibiting amicronodular surface, coupling agents should be utilized in conjunctionwith mica. The function of the coupling agent is to promote theadherence of the polypropylene moiety to mica. In the absence of acoupling agent, mica may not adhere well to the polymer matrix and somay not be integrated into the sheet from which the containers, bowls,trays and plates are thermoformed. Maleic anhydride and acrylic modifiedpolypropylenes are suitable coupling agents.

The containers, bowls, trays and plates of this invention are preferablyformed from a sheet which has been extruded as shown in FIG. 1 and thenthermoformed as shown in FIG. 2.

Advantageously, the sheet is formed by an extrusion process utilizingthe compounded polymer/mica mixtures. The final extrusion processrenders a sheet with excellent thermal properties and cut resistance.Generally, injection molding is inherently not suitable for themanufacture of self-texturized micronodular containers, bowls, trays andplates since injection molded products are smooth plastic like articleswhich do not exhibit a micronodular surface or have a feel of stonewareor pottery-like look.

The aesthetically pleasing disposable microwaveable containers, trays,bowls and plates exhibit (a) at least one micronodular surface, thissurface is usually on the food contact side of the plate or container,and (b) a melting point of at least 250° F. In addition, the containeror plate is dimensionally stable and resistant to grease, sugar, andwater at temperatures of at least 220° F. and is of sufficient toughnessto be resistant to cutting by serrated polystyrene flatware. The micafilled polypropylene plates also exhibit a thickness uniformitycharacterized by a thickness coefficient of variation of less than aboutfive percent.

Mica is a common name for naturally occurring inert mineral of thephyllosilicate chemical family, specifically potassium aluminosilicatewhereby the aluminum ions may be partially replaced by iron andmagnesium and part of the chemically bound water may be substituted byfluorine.

Mica is easily cleaved into thin, relatively regular, flexible yetstrong sheets (leaf-like flakes) with thickness in the range of half amicron and aspect ratio as high as 300. Mica is much softer than otherinorganic fillers (calcium carbonate, wollastonite, glass) yet onlyslightly harder than talc. Mica has a slippery tactile feel and lowabrasiveness relative to other common inorganic fillers.

The reinforcement effect at 40 weight percent mica is equivalent to thatof 30 weight percent glass fiber. But hard inorganic fibrous fillerssuch as glass (various lengths) and wollastonite (acicular structures)have serious drawbacks such as abrasiveness and are prone to fracturedegradation during conventional melt processing. Other fibrous (organic)fillers are derived from wood and vegetable sources and are not suitablefor use in the manufacture of the containers of this invention since theorganic fillers tend to degrade during processing and they are alsomoisture sensitive. In our process we prefer to use about 20 to 35weight percent mica.

Extenders such as calcium carbonate and clay have been traditionallyused in disposable plastic foodservice articles with low cost as theprimary concern, i.e., these fillers are usually selected for costreduction rather than reinforcement. For example, calcium carbonate is acheap, hard, and abrasive filler which delivers moderately lowreinforcement (even when coupled) due to its low aspect ratio and highlyirregular particle structure. In the case where microwaveability isdesired for the plastic disposable foodservice article, the not soperfect solution has been the use of relatively expensive high heatpolystyrene based materials (e.g., unfilled PPO and SMA engineeringresins), where PPO refers to polyphenylene oxide and SMA refers tostyrene-maleic anhydride copolymer.

The mica filled polypropylene containers, bowls, trays and plates ofthis invention have overcome the disadvantages of the prior art typecontainers, bowls, trays and plates and are significantly superior tothem.

Platy mineral filled polypropylene is compounded by pre-blending thepolypropylene in pellet or flake form with mica powder and otheradditives (coupling agents, color concentrates, pigments, antioxidants,lubricants, nucleating agents, antistatic agents, etc.). This mixture isconveyed into the feed section addition point of a twin screwcompounding extruder. Alternatively, the components are advantageouslyfed separately into the same or at different points of addition, usingcombinations of volumetric and/or gravimetric (i.e., loss in weighttype) feeders.

For white pigmentation, titanium dioxide is preferred due to combinationof brightness, and opacity, as well as stability during processing andfinal use. Surface treatment may be optionally used to further enhancewetting, dispersion, compatibility with matrix resins whereas thetitanium dioxide forms may be of the rutile or anatase type. Alternatewhite pigments may also consist of calcined clay or blends of calcinedclay with titanium dioxide. For black pigmentation, carbon black ispreferred due to a combination of desirable characteristics such asblackness, and dispersibility, the latter of which can be carefullycontrolled by choice of particle size and surface chemistry. Carbonblack is amorphous carbon in finely divided form which is made by eitherthe incomplete combustion of natural gas (channel black) or by reductionof liquid hydrocarbons in refractory chambers (furnace black).

The twin screw extruder provides sufficient mixing action to effectivelycause the wetting and dispersion of the filler into the polymer matrix.The twin screw extruder may be of the co-rotating or counter-rotatingtype, where each type is equipped with different screw flight elementswhich are appropriate for the feed, mixing, and melt metering zones. Thedischarge zone normally consists of a strand die where the exitingmolten material strands are quenched in a circulating water bathfollowed by knife cutting into pellets.

Low molecular weight additives such as waxes, fluorinated polymers, andother specialty lubricants are suitably used as process aids to reducethe melt viscosity and improve throughput. Other additives may includenucleating agents and antistatic agents. Antioxidants may be added insmall amounts, generally less than one weight percent, to minimize shearand thermal degradation of the polypropylene during the extrusion andforming processes as well as to promote the chemical stability of thesheet prior to and during final article use. Suitable antioxidants areadvantageously selected from the group of phenolics and phosphites andblends thereof. These are produced by Ciba-Geigy and General ElectricCorporation.

Coupling agents such as silanes (azido functional or amido styrylfunctional), organofunctional silicone compounds, chlorinatedhydrocarbons with and without silane, in situ polymerization ofmonomers, or modified polyolefins are often used. For certainapplications, the mica particle surfaces may be pretreated with thecoupling agents. For the polymeric coupling agents or compatibilizers,in particular, such agents may be conveniently added directly during theformulation compounding step. Polymeric compatibilizers are preferredfor ease of handling and also for the avoidance of toxic residualmonomers and solvents. In particular, maleic anhydride or acrylicmodified polypropylene can be used as coupling agents. They promote theadherence between the polypropylene and the mica filler and serve tominimize the embrittlement effect of the filler, and also promotetoughness at ambient conditions and dimensional stability at elevatedtemperatures for the platy mineral filled sheets and the containers madetherefrom. The use of maleic anhydride modified polypropylene, wherebythe maleic anhydride is in the range of 0.5-5.0 mole percent, ispreferred. The use of coupling agents promotes good interfacial bondingbetween the platy mineral filler and the matrix resin interfaceresulting in good solid state mechanical properties of the containersand plates. The coupling agents also maximize the melt strengthenhancing features of the platy mica filler. Melt strength of the sheetsis further improved when the mica mixtures are used as a filler sincesaid filler serves to provide "inter-particle connectivity" or physicalcrosslinking.

SSI rigidity is measured with the Single Service Institute PlateRigidity Tester originally available through Single Service Institute,1025 Connecticut Ave. NW, Washington D.C. This test is designed tomeasure the rigidity (i.e. resistance to buckling and bending) of singleservice paper and plastic plates, bowls, dishes, and trays by measuringthe force required to deflect the rim of these products a distance of0.5 inch while the product is supported at its geometric center.Specifically, the plate specimen is held by a spring loaded clamp on oneside and is center fulcrum supported. The rim or flange side opposite tothe clamped side is subjected to 0.5 inch deflection by means of amotorized cam assembly equipped with a load cell, and the force (grams)is recorded. SSI rigidity is expressed as grams per 0.5 inch deflection.A higher SSI value is desirable since this indicates a more rigidproduct. All measurements were done at room temperature and geometricmean averages for the machine and cross machine direction are reported.As shown in FIG. 3, Fort James's containers and plates of this invention(designation J) have a higher SSI rigidity than commercial platesmanufactured by Solo Cup Company (designation S) at equal or lower cost.

Plastic cast sheet extrusion equipment is suitable for the manufactureof multilayered or single layered mica filled sheets of a polyolefinselected from the group consisting of polypropylene, polypropylenepolyethylene copolymer or blend, and mixtures of these.

The use of coupling agents promotes good interfacial bonding between theplaty mineral filler and the matrix resin interface resulting in goodsolid state mechanical properties of the containers and plates. Thecontainers in the form of a 8.75-inch plate at a basis weight of aboutat least 175 pounds per 3000 square foot ream have a SSI rigidity of atleast 250 grams per 0.5 inches. For 10.25-inch plates at a basis weightof about 280 pounds per 3000 square foot ream, the SSI rigidity is atleast about 400 grams per 0.5 inches. In plates of this invention, thebasis weight is determined from the micronodular surface. At a basisweight of about 130, the SSI rigidity is about 200 grams per 0.5 inchand at a basis weight of about 360 the SSI rigidity is about 700 gramsper 0.5 inch. The coupling agents also maximize the melt strengthenhancing effect of the platy inorganic mineral filler. Melt strength ofthe sheets is further improved when mica is used as a filler sincegeometry of the mineral in the form of high aspect ratio flakes servesto provide "inter-particle connectivity" or physical crosslinking.

In FIG. 1 a process is shown for the manufacture of a single layer micafilled polypropylene sheet. Previously compounded and pelletizedmixtures of polypropylene, mica, and other additives are gravity fed bya hopper (10) into the feed zone of a single screw extruder system.Primary extruder (11) has a 2 inch diameter screw with a 24/1 length todiameter ratio. Optionally, multilayer coextruded sheet can be producedby utilizing at least one additional single screw extruder (12, 13, 14)in conjunction with a combining feedblock with proper melt piping andmanifold arrangements. Suitably one to seven screw extruders areemployed, preferably three. A flexible lip flat sheet die (15) having awidth of 31 inches was used.

The sheet of this invention (16) enters the sheet takeoff portion (i.e.,after the molten material exits the die) comprising a three-rollpolishing/casing unit (17) with individually temperature controlledrolls, a two-rubber roll sheet pull unit (18), and a dual turret, dualshaft winder, whereby only one shaft winder roll (19) may be used. Thethree takeoff units were mechanically tied together, were on a commontrack, and can be automatically traversed from close die lip proximityto about 36 inch distant. During the extrusion process, the distancebetween the die exit and the casting unit were maintained at 2 inches.These three chrome rolls comprising the sheet casting unit areindividually temperature controlled by integral oil circulating pumpsand heat exchangers and nip gaps are adjustable. A speed differentialbetween cast rolls and pull rolls is normally maintained such that pullroll speed is approximately within ten percent (10%) of cast roll speed.Achievable line speeds are in the range of 1-12.5 feet per minute, whilefor a sheet on the order of 20 mil thick, the line speed is about 5-6feet per minute. The sheet is wound on a roll (19). Table 1 shows thesheet process conditions employed for the sheet extrusion of mica filledpolypropylene and the unfilled polypropylene control. These sheetssuitably have a basis weight of about 200 to 950, per 3000 square footream preferably about 200 to 400 per 3000 square foot ream.

Thermoforming is the pressing or squeezing of pliable material intofinal shape. In the simplest form, thermoforming is the draping of asoftened sheet over a shaped mold. In the more advanced form,thermoforming is the automatic, high speed positioning of a sheet havingan accurately controlled temperature into a pneumatically actuatedforming station whereby the article's shape is defined by the mold,followed by trimming and regrind collection.

Forming techniques other than conventional thermoforming are alsosuitable for the manufacture of articles described in the presentinvention. These include variations such as presoftening the extrudedsheet to temperatures below the final melting temperature, cutting flatregions (i.e., blanks) from the sheet, transfer of blanks by gravity ormechanical means into matched molds whereby the blanks are shaped intothe article by heat and pressure. The sheet from which the blanks havebeen cut out is collected as regrind and is recyclable. Conventionalpaperboard pressing equipment and corresponding forming tooling isoptionally modified to produce articles of this invention.

The extruded sheet used in the suitable forming, and thermoformingprocess, or the preferred thermoforming process as shown in FIG. 2 has athickness of about 0.010 to 0.080 inches, suitably 0.010 to 0.050inches. For plates the preferred thickness is about 0.015 to 0.025inches. Suitable mica filler loading level in the extruded sheet is inthe range of 10 to 60 weight percent, more preferably 20-50 weightpercent, most preferably 20 to 35 weight percent. The mica flake aspectratio is in the range of 30-300, more preferably 15-250, with particlesize range of about 10 to 500 microns. The extruded sheet comprisesisotactic polypropylene homopolymer or polypropylene polyethylenecopolymer or blend or a mixture of these as base resin, preferablyhaving a melt flow index in the range 0.1-5.0, more preferably 0.2-2.0.Propylene copolymers or blends with ethylene levels in the range of 1-10mole percent, more preferably 2-5 mole percent, are optionally used.

The preferred type of mica is muscovite, which is the most common formin commerce. Optionally other less common mica types such as phlogopite,biotite, and fluorphlogopite are used. Although there are an infinitenumber of compositions possible for these four generic types due toisomorphous substitution which are mine specific, the selection ofparticular grades is driven by particle aspect ratio, particle size,price, and availability.

The melt flow rate (MFR) or melt index is a common and simple method fordetermining the flow properties of molten polymers. Resin is introducedand melted in a cylindrical space. After temperature equilibration isreached, a weight is used to push a plunger vertically downward wherebythe resin is extruded through a narrow orifice. The usual testtemperature for polypropylene is 230° C. and the load is 2.16 Kg.Extruded material is collected and weighed and the time required toextrude a specific weight is recorded. MFR is expressed as grams per 10minutes, which is the weight of material extruded in a 10 minute timeperiod. MFR is inversely proportional to both polymer viscosity andpolymer molecular weight.

The extruded sheet comprises coupling agents, preferably modifiedpolypropylene, suitable modifiers are maleic anhydride or acrylicmodified polypropylene. The maleic anhydride or acrylic modifiedpolypropylene comprises about 0.5 to 3 weight percent of total sheetcomposition.

Suitably the extruded sheet comprises coloring agents for aestheticappeal, preferably titanium dioxide, carbon black, and other opacifyingagents in the range of 0.5-8 weight percent based on total composition,preferably 2.5 to 6.5 weight percent. The extruded sheet comprises minoramounts of other additives such as lubricants and antioxidants. Thesearticles of manufacture may be suitably colored with pigments or dyes.Pigments are defined as small insoluble organic or inorganic particlesdispersed in the resin medium to promote opacity or translucency. Usualpigments include carbon black, titanium dioxide, zinc oxide, ironoxides, and mixed metal oxides. Dyes are organic and soluble in theplastic, and may be used alone or in combination with pigments tobrighten up pigment based colors. All such colorants may be used in avariety of modes which include dry color, conventional colorconcentrates, liquid color and precolored resin.

Mica filled polypropylene sheets are suitably formed into plates, bowls,cups, trays, buckets, souffle dishes, and containers using a forming orthermoforming process disclosed herein. In the preferred process, thesearticles of manufacture and containers are made using the Comet StarlettThermoformer Unit. This machine is capable of vacuum forming productsfrom heat softened thermoplastic materials and is schematically depictedin FIG. 2. Sheet portions (23) having dimensions of 17.5 inches by 16.25inches were clamped on two opposing sides and inserted into an oven (22)equipped with upper (20) and lower (21) heaters, whereby heater inputsettings were in the range of 20-30 percent and hold times were on theorder of 60-80 seconds. Under these conditions, the oven air temperatureas recorded by a digital thermocouple was in the range of 221° F. to225° F., while the sheet surface temperature, as recorded by adheringindicator thermocouples, was approximately 330° F. to 340° F.

When the clamped and heat softened sheet (23) exits the oven (22), itmay be vacuum formed by either procedure (A) or (B), both of whichutilize only one mold which is fabricated from epoxy thermosetmaterials. Mode (A) uses a male mold (24) whereby the sheet is sucked upto conform to it by means of vacuum where the vacuum ports are presenton the mold base as well as on the periphery side of the container(i.e., flange area). Mode (B) arrangement is such that the vacuumdirection is opposite to mode (A), where again vacuum holes are locatedaround the base and periphery. In the case of mode (B), a female mold(25) is used, and this arrangement is preferred since the air side ofthe sheet corresponds to the food contact side. The food contact sideundergoes a beneficial texturizing effect as a result of the heattreatment, whereby the resin flows around and outward from the micaparticles close to the surface causing the mineral to become moreexposed which creates a micronodular surface as manifested by decreasedgloss and increased surface roughness. The micronodular surface givesthe container a stoneware or pottery-like appearance. This feature canbe reasonably seen by reviewing FIG. 22 where the micronodular structureof the plate is clearly shown in the black and white scanning electronphotomicrograph while the neat extruded sheet exhibits no suchmicronodular surface. The photomicrograph was obtained from a 10×15 mmpiece cut out of the plate bottom. The sheet sample was mounted withsurface of interest up on a specimen stub, and coated withgold/palladium. The stub was placed in a JEOL 840A Scanning ElectronMicroscope (SEM). Photomicrographs of the samples were taken at75×magnification, 30 degree tilt, 39 mm working distance at 3 kv.

Suitably a process for forming a microwaveable, food contact compatible,disposable, rigid and strong, mica-filled polyolefin container, plate,bucket, etc., wherein the polyolefin is selected from polypropylene,polypropylene polyethylene copolymer or blend comprise the steps of:

(a) forming an extrudable admixture of the polyolefin resin and mica;

(b) extruding said extrudable admixture of the polyolefin resin and micaat elevated temperature;

(c) passing the resulting extruded admixture of the polyolefin resin andmica through a multiple roll stack, at least one roll of said roll stackhaving a matte finish;

(d) passing said extruded admixture of the polyolefin resin and mica atleast partially around said roll having a matte finish;

(e) controlling the speed of said extrusion process, the size,temperature and configuration of said roll stack such that the surfaceof said extruded admixture of polyolefin resin and mica not in contactwith said matte roll has a coarse-grained structure; and

(f) thermoforming said extruded admixture of polyolefin, resin, and micaand recovering a container, plate, bucket, etc., having a micronodularsurface and a rough surface, exhibiting a melting point of no less thanabout 250° F.; said container, plate, bucket, etc., being dimensionallystable and resistant to grease, sugar, and water at temperatures up toabout 220° F. and having sufficient toughness to be resistant to cuttingby serrated flatware.

Advantageously, the coarse-grained structure of the surface of saidextruded admixture of polyolefin resin and mica not in contact with saidmatte roll is formed by transversing the extruded admixture of thepolyolefin resin and mica through a curvilinear path and at leastpartially solidifying the surface of said extruded admixture ofpolyolefin resin and mica not contacting said matte roll while thatsurface is in tension relative to the surface contacting said matteroll.

Preferably a process for forming a mica-filled polypropylene container,plate, bucket, tray, bowl, etc., comprises the steps of:

(a) forming an extrudable admixture of the polypropylene resin and mica;

(b) extruding said extrudable admixture of the polypropylene resin andmica at elevated temperature;

(c) passing the resulting extruded admixture of the polypropylene resinand mica through a multiple roll stack, at least one roll of said rollstack having a matte finish;

(d) passing said extruded admixture of the polypropylene resin and micaat least partially around said roll having a matte finish;

(e) controlling the speed of said extrusion process, the size,temperature and configuration of said roll stack such that the surfaceof said extruded admixture of the polypropylene resin and mica incontact with said matte roll has a matted structure; and

(f) thermoforming said extruded admixture of polypropylene, resin, andthe mica and recovering a container, plate, bucket, etc., having amicronodular surface and exhibiting a melting point of no less than 250°F., said container, plate, bucket, etc. being dimensionally stable andresistant to grease, sugar, and water at temperatures up to about 220°F. and having sufficient toughness to be resistant to cutting byserrated flatware.

A process for forming a mica-filled polypropylene sheet suitable forthermoforming micronodular containers and plates comprises the steps of:

(a) forming an extrudable admixture of the polypropylene resin and mica;

(b) extruding said extrudable admixture of the polypropylene resin andmica at elevated temperature;

(c) passing the resulting extruded admixture of the polypropylene resinand mica through a multiple roll stack, at least one roll of said rollstack having a matte finish;

(d) passing said extruded admixture of the polypropylene resin and micaat least partially around said roll having a matte finish;

(e) controlling the speed of said extrusion process, the size,temperature and configuration of said roll stack such that the surfaceof said extruded admixture of the polypropylene resin and mica not incontact with said matte roll has a coarse structure; and

(f) the surface in contact with the matte roll has a matted surface; and

(g) recovering a sheet having a matted surface and a coarse surface saidsheet comprising polypropylene and mica moieties. In this process thepolypropylene may be partially replaced with polypropylene polyethylenecopolymer or blend. Usually the copolymer compresses less than ten molepercent of the total polyolefin content of the sheet.

Advantageously, other thermoforming arrangements are suitable and may bepreferred in conventional sheet and web feed thermoforming commercialproduction operations. Alternative arrangements include the use ofdrape, vacuum, pressure, free blowing, matched die, billow drape, vacuumsnap-back, billow vacuum, plug assist vacuum, plug assist pressure,pressure reverse draw with plug assist vacuum, reverse draw with plugassist, pressure bubble immersion, trapped sheet, slip, diaphragm,twin-sheet cut sheet, twin-sheet rollfed forming or any suitablecombinations of the above. Details are provided in J. L. Throne's book,Thermoforming, published in 1987 by Coulthard. Pages 21 through 29 ofthat book are incorporated herein by reference. Suitable alternatearrangements also include a pillow forming technique which creates apositive air pressure between two heat softened sheets to inflate themagainst a clamped male/female mold system to produce a hollow product.Metal molds are etched with patterns ranging from fine to coarse inorder to simulate a natural or grain like texturized look. Suitablyformed articles are trimmed in line with a cutting die and regrind isoptionally reused since the material is thermoplastic in nature. Otherarrangements for productivity enhancements include the simultaneousforming of multiple articles with multiple dies in order to maximizethroughput and minimize scrap.

The sheet of the present invention is suitably formed into plates orbowls having a circular configuration. These articles of manufacture mayalso be square or rectangular in shape having angular corners, such asfound in a tray. Further, additional shapes such as triangular,multi-sided, polyhexal, etc., are contemplated including compartmentedtrays and plates as well as oval platters. In each contemplatedembodiment, all corners are rounded or curved with the preferredembodiment of the present invention being depicted in FIGS. 5 through21.

The description of FIGS. 5 through 21 is illustrative of the presentinvention, but it should be understood that these figures are notintended to limit the invention and that various changes may be made bythose skilled in the art without changing the essential characteristicsand basic concept of the invention. In one embodiment of this inventionthe plates have the DIXIE® Superstrong profile as illustrated in FIGS. 5through 8 and also described in U.S. Pat. No. 5,326,020 assigned to theassignee of the present invention and incorporated herein by referenceinto this application. These containers also may have other featuressuch as ridges, emboss, and deboss patterns suitable for enhancing theproperties of the containers of this invention.

Throughout the following description, each of the dimensions arereferenced with respect to a given diameter D which in, accordance withthe present invention as illustrated in FIGS. 6 and 7, is approximately8.75 inches. However, the particular diameter of the container is not acritical limitation and is only set forth herein by way of example. Itis the relationship between the various portions of the rimconfiguration which are essential.

The planar inner region (61) in accordance with the illustratedembodiment in FIGS. 5 through 8 has a radius X1 which is equal toapproximately 0.3 D-0.4 D and preferably 0.348 D. Adjoining an outerperiphery of the planar inner region (61) is a sidewall portion (60)including annular region (63) having a radius of curvature equal toapproximately 0.05 D-0.06 D and preferably 0.0572 D with the centerpoint thereof being positioned a distance Y1 from the planar innerregion (61). Included angle (70) of the annular region (63) is fromabout 40° to about 70° and preferably about 60°-65° or approximately62°. Adjoining the periphery of the annular region (63) is the firstfrusto-conical region (64) which slopes upwardly at an angle A1 withrespect to the vertical from about 20° to about 35° and preferably about25°-30° or approximately 27.50. Additionally, the frusto-conical region(64) is of a length greater than about 0.015 D, preferably from about0.025 D to 0.05 D and more preferably approximately 0.036 D. Further,adjoining the first frusto-conical region (64) is the arcuate annularregion (65) which includes a radius of curvature in the range of 0.015 Dto 0.03 D and preferably approximately 0.024 D with the center pointthereof being positioned a distance Y2 from the planar inner region(61). The included angle (71) of the arcuate annular region (65) mayrange from about 61° to about 82° and is preferably 66° to 77° or about73°. The second portion (67) of the arcuate annular region (65), that isthe distal portion of the arcuate annular region (65), is positionedsuch that a line tangent to the curvature of the arcuate annular region(65) at the second portion (67) slopes downwardly and outwardly at anangle of approximately 0° to 12°.

The combination of the annular region (63) and arcuate annular region(65) should combine to position the second portion (67) of the arcuateannular region (65) in the manner set forth herein above. That is, theincluded angle (70) of the annular region (63) when combined with theincluded angle (71) of the arcuate annular region (65) with the firstfrusto-conical region (64) spanning therebetween, positions the secondportion (67) of the arcuate annular region (65) in a manner such thatthe second frusto-conical region (68), which extends substantiallytangentially from the distal end of the second portion (67) of thearcuate annular region (65) extends outwardly and downwardly at an angleof about 0° to 12°. The second frusto-conical region (68) is of a lengthin a range from about 0.03 D to about 0.05 D and is preferably 0.04 D.Because the second frusto-conical region (68) extends substantiallytangentially from the second portion (67) of the arcuate annular region(65), the second frusto-conical region (68) extends outwardly anddownwardly at an angle A3 in the range from approximately 0° to 12° withrespect to a horizontal plane formed by the planar inner region (61).

Adjoining an outer periphery of the second frusto-conical region (68) isthe lip (69) which is in the form of yet another frusto-conical regionwhich extends outwardly and downwardly from the second frusto-conicalregion (68). The lip (69) is of a length of at least 0.005 D and ispreferably approximately 0.010 D. Further, the lip (69) extends at anangle A2 of no more than 45° from vertical, preferably approximately 15°to 30° with respect to the vertical plane.

At the transition between the second frusto-conical region (68) and thelip (69) is a transition region (72). The transition region (72)includes a radius of curvature R3 which is in the range of about 0.008 Dand 0.01 D and is preferably approximately 0.0092 D with the centerpoint thereof being positioned a distance Y3 from the planar innerregion (61). Additionally, the transition region (72) has an includedangle A4 of approximately 48° to 70°. The plates disclosed in FIGS. 9through 12 have the dimensions of the plates disclosed in U.S. Pat. No.5,088,040 and incorporated herein by reference in its entirety. Thesecontainers may have other features such as ridges, emboss, and debosspatterns suitable for enhancing the properties of the containers of thisinvention.

The description of FIGS. 13 through 16 is illustrative of the presentinvention, but it should be understood that these figures are notintended to limit the invention and that various changes may be made bythose skilled in the art without changing the essential characteristicsand basic concept of the invention. In one embodiment of this inventionthe trays have either the DIXIE® Superstrong profile as illustrated inFIGS. 13 through 16 and also described in U.S. Pat. No. 5,326,020assigned to the assignee of the present invention and incorporatedherein by reference into this application. These trays may have otherfeatures such as ridges, emboss, and deboss patterns suitable forenhancing the properties of the trays of this invention. Arepresentative tray is illustrated in FIGS. 13 through 16. Throughoutthe following description, each of the dimensions are referenced toeither the length D1 or the width D2, which in accordance with thepresent invention as illustrated in FIGS. 13 through 16 areapproximately 10.90 and 8.00 inches respectively. D1 is larger than orequal to D2. However, the particular length and width of thesecontainers is not a critical limitation and is only set forth herein byway of example. It is the relationship between the various portions ofthe rim configurations which are essential. The planar inner region(101) in accordance with the illustrated embodiment in FIGS. 13 and 14,has a length X1 which is equal to approximately 0.3 D1 to 0.4 D1 and 0.3D2 to 0.4 D2 and preferably 0.354 D1 and preferably 0.342 D2. Adjoiningan outer periphery of the planar inner region (101) is a sidewallportion (100) including annular region (103) having a radius ofcurvature equal to approximately 0.02 D1 to 0.03 D1 and 0.025 D2 to0.035 D2 and preferably 0.023 D1 and 0.031 D2 with the center pointthereof being positioned a distance Y1 from the planar inner region(101). Included angle (110) of the annular region (103) is from about40° to about 80° and preferably about 65° to 75° or approximately 69°.Adjoining the periphery of the annular region (103) is the firstfrusto-conical region (104) which slopes upwardly at an angle A1 withrespect to the vertical from about 10° to about 50° and preferably about15° to 25° or approximately 21°. Additionally, the frusto-conical region(104) is of a length greater than about 0.05 D1 and 0.055 D2, preferablyfrom about 0.1 D1 to 0.2 D1 and 0.15 D2 to 0.25 D2 and more preferablyapproximately 0.15 D1 and 0.19 D2. Further, adjoining the firstfrusto-conical region (104) is the arcuate annular region (105) whichincludes a radius of curvature in the range of 0.005 D1 to 0.007 D1 and0.007 D2 to 0.009 D2 and preferably approximately 0.006 D1 and 0.008 D2with the center point thereof being positioned a distance Y2 from theplanar inner region (101). The included angle (111) of the arcuateannular region (105) may range from about 40° to about 92° and ispreferably 65° to 87°. The second portion (107) of the arcuate annularregion (105), that is the distal portion of the arcuate annular region(105) is positioned such that a line tangent to the curvature of thearcuate annular region (105) at the second portion (107) slopesdownwardly and outwardly at an angle of approximately 0° to 12°.

The combination of the annular region (103) and arcuate annular region(105) should combine to position the second portion (107) of the arcuateannular region (105) in the manner set forth herein above. That is, theincluded angle (110) of the annular region (103) when combined with theincluded angle (111) of the arcuate annular region (105) with the firstfrusto-conical region (124) spanning therebetween, positions the secondportion (107) of the arcuate annular region (105) in a manner such thatthe second frusto-conical region (108), which extends substantiallytangentially from the distal end of the second portion (107) of thearcuate annular region (105) extends outwardly and downwardly at anangle of about 0° to 12°. The second frusto-conical region (108) is of alength in a range from about 0.045 D1 to about 0.055 D1 and 0.030 D2 toabout 0.040 D2 and is preferably 0.052 D1 and 0.034 D2. Because thesecond frusto-conical region (108) extends substantially tangentiallyfrom the second portion (107) of the arcuate annular region (105), thesecond frusto-conical region (108) extends outwardly and downwardly atan angle A3 in the range from approximately 0° to 12° with respect to ahorizontal plane formed by the planar inner region (161).

Adjoining an outer periphery of the second frusto-conical region (104)is the lip (109) which is in the form of yet another frusto-conicalregion which extends outwardly and downwardly from the secondfrusto-conical region (108). The lip (109) is of a length of at least0.006 D1 and 0.009 D2 and is preferably approximately 0.010 D1 and 0.013D2. Further, the lip (109) extends at an angle A2 of no more than 45°from vertical, preferably approximately 10° to 30° with respect to thevertical plane and more preferably approximately 20°.

At the transition between the second frusto-conical region (108) and thelip (109) is a transition region (112). The transition region (112)includes a radius of curvature R3 which is in the range of about 0.005D1 to 0.007 D1 and 0.007 D2 to 0.009 D2 and is preferably approximately0.006 D1 and 0.008 D2 with the center point thereof being positioned adistance Y3 from the planar inner region (21). Additionally, thetransition region (112) has an included angle A4 of approximately 48° to80°.

The description of FIGS. 17 through 20 is illustrative of the presentinvention, but it should be understood that these figures are notintended to limit the invention and that various changes may be made bythose skilled in the art without changing the essential characteristicsand basic concept of the invention. In one embodiment of this inventionthe bowl is illustrated in FIGS. 17 through 20. These containers mayhave other features such as ridges, emboss, and deboss patterns suitablefor enhancing the properties of the containers of this invention.Throughout the following description, each of the dimensions arereferenced with respect to a given diameter D which, in accordance withthe present invention as illustrated in FIGS. 17 through 20, isapproximately 7.5 inches. However, the particular diameter of thecontainers is not a critical limitation and is only set forth herein byway of example. It is the relationship between the various portions ofthe rim configuration which are essential. The planar inner region (131)in accordance with the illustrated embodiment in FIGS. 17 through 20,has a radius X1 which is equal to approximately 0.2 D to 0.3 D andpreferably 0.25 D. Adjoining an outer periphery of the planar innerregion (131) is a sidewall portion (130) including annular region (133)having a radius of curvature equal to approximately 0.05 D to 0.15 D andpreferably 0.11 D with the center point thereof being positioned adistance Y1 from the planar inner region (131). Included angle (141) ofthe annular region (133) is from about 45° to about 75° and preferablyabout 60° to 70° or approximately 65°. Adjoining the periphery of theannular region (133) is the first frusto-conical region (134) whichslopes upwardly at an angle A1 with respect to the vertical from about15° to about 45° and preferably about 20° to 30° or approximately 25°.Additionally, the frusto-conical region (134) is of a length greaterthan about 0.1 D, preferably from about 0.17 D to 0.19 D and morepreferably approximately 0.18 D. Further, adjoining the firstfrusto-conical region (134) is the arcuate annular region (135) whichincludes a radius of curvature in the range of 0.015 D to 0.030 D andpreferably approximately 0.023 D with the center point thereof beingpositioned a distance Y2 from the planar inner region (131). Theincluded angle (142) of the arcuate annular region (135) may range fromabout 45° to about 87° and is preferably 60° to 77°. The second portion(137) of the arcuate annular region (135), that is the distal portion ofthe arcuate annular region (135) is positioned such that a line tangentto the curvature of the arcuate annular region (135) at the secondportion (137) slopes downwardly and outwardly at an angle ofapproximately 0° to 12°.

The combination of the annular region (133) and arcuate annular region(135) should combine to position the second portion (137)of the arcuateannular region (131) in the manner set forth herein above. That is, theincluded angle (130) of the annular region (133) when combined with theincluded angle (131) of the arcuate annular region (135) with the firstfrusto-conical region (134) spanning therebetween, positions the secondportion (137) of the arcuate annular region (135) in a manner such thatthe second frusto-conical region (138), which extends substantiallytangentially from the distal end of the second portion (137) of thearcuate annular region (135) extends outwardly and downwardly at anangle of about 0° to 12°. The second frusto-conical region (138) is of alength in a range from about 0.02 D to about 0.04 D and is preferably0.03 D. Because the second frusto-conical region (138) extendssubstantially tangentially from the second portion (137) of the arcuateannular region (135), the second frusto-conical region (138) extendsoutwardly and downwardly at an angle A3 in the range from approximately0° to 12° with respect to a horizontal plane formed by the planar innerregion (131).

Adjoining an outer periphery of the second frusto-conical region (134)is the lip (139) which is in the form of yet another frusto-conicalregion which extends outwardly and downwardly from the secondfrusto-conical region (138). The lip (139) is of a length of at least0.01 D and is preferably approximately 0.017 D. Further, the lip (139)extends at an angle A2 of no more than 45° from vertical, preferablyapproximately 10° to 30° with respect to the vertical plane and morepreferably approximately 25°.

At the transition between the second frusto-conical region (138) and thelip (139) is a transition region (143). The transition region (143)includes a radius of curvature R3 which is in the range of about 0.007 Dand 0.012 D and is preferably approximately 0.009 D with the centerpoint thereof being positioned a distance Y3 from the planar innerregion (131). Additionally, the transition region (142) has an includedangle A4 of approximately 48° to 80°.

The description of FIG. 21 is illustrative of the present invention, butit should be understood that this figure is not intended to limit theinvention and that various changes may be made by those skilled in theart without changing the essential characteristics and basic concept ofthe invention. The containers of this invention may be formed astake-out containers, and as a representative embodiment, a suitabletake-out container, will now be described in general with respect toFIG. 21 wherein the lid and base formed as described in U.S. Pat. No.5,377,860 and incorporated herein by reference is illustrated. While thecontainer illustrated in FIG. 21 is oblong in configuration, thecontainer may be round, oval, substantially rectangular or square asdictated by the contents which are to be placed within the container.The container (30) is formed of a base or bottom portion (31) and a lid(32). The lid (32) includes radially extending opening tabs (33) whichcooperate with the radially extending opening tabs (34) of the base (31)in order to allow the consumer to readily open the sealed container. Thebase (31) of the container (30) includes a substantially planar bottom(35) and a substantially vertically extending peripheral sidewall (36).Integrally connected to the upstanding sidewall (31) is a sealing brim(37) which is received within a cooperating sealing brim (38) of the lid(32).

The lid (32) includes a substantially planar top portion (39) and a rim(40) extending about a periphery of the top portion (39). The rim (40)is provided in order to enhance the strength of an extended volumeportion (41) of the lid (32). The rim (40) also serves to locate thebase (31) on the lid when the lid is used as a stand.

The extended volume portion (41) is formed by extension wall (42)positioned about the perimeter of the rim (40) and extending downwardlytherefrom. The extension wall (42) is integrally formed with ahorizontal lid reinforcing ring (43) which is substantially parallel tothe top portion (39) of the lid (32). The outer perimeter of the lidreinforcing ring (43) is further integrally formed with the sealing brim(38). Also, extending radially outward from the sealing brim (38) is asecond horizontal lid reinforcing ring (44) which extends substantiallyparallel to the top portion (39) as well.

Similarly, the base (31) includes a horizontal lid reinforcing ring (45)which extends from the periphery of the sealing brim (37) for aiding inand maintaining the structural integrity of the sealing brim (37) aswell as the container (30) as a whole. In addition to the reinforcingring (45), a step (46) may be provided about an upper portion of theperipheral sidewall (36) for preventing nested units from becomingjammed together due to excessive interpenetration when stacked andnested. Also, formed in an upper portion of the sidewall (36) areundercuts (47) which cooperate with detents (48), only one of which isillustrated in FIG. 21 at the integral connection between a brim (38)and lid reinforcing ring (43). The detents, when engaged in theundercuts (47), provide an audible indication that the container is infact sealed. Additionally, undercuts (49) may be provided in an outerperiphery of the brim (37) for receiving detents (50) formed in an outerportion of the brim (38) for again providing an audible indication thatthe container is sealed. While the container illustrated in FIG. 21shows detents and undercuts formed in both the inner and outer portionsof the brims (47) and (38), respectively, it may be desired to providerespective detents and undercuts on only one side of the brim or toprovide no undercuts and detents on either side of the brim.

The Parker Roughness method was used to determine roughness using theMessmer Parker Print-Surf Roughness. Operation procedure details arereferenced in the Messmer Instruments Ltd. user manual for theinstrument (Model No. ME-90) which is distributed by Huygen Corporation.The flat specimen is clamped under 1 Mpa pressure against a narrowannular surface by a soft backing and the resistance of air flow of thegap between the specimen and the annulus is measured. The air flow isproportional to the cube of the gap width and the roughness is expressedas the root mean cube gap in units of micrometers. Higher Parkerroughness values indicate higher degrees of surface roughness. Gloss isreported as "gloss units at 75 or 60 degrees." Gloss measurements wereconducted following TAPPI Standard Method T480-OM 92.

Hunter color L, a, and b parameters were measured using TAPPI Method T524 OM-94. The symbols L, a, b designate color values as follows: Ldenotes lightness increasing from zero for black to 100 for perfectwhite; a shows redness when plus, greenness when minus, and zero forgray; and b represents yellowness when plus, blueness when minus, andzero for gray.

Whiteness index was measured according to procedures outlined in thepublication "Measurement and Control of the Optical Properties of Paper"by Technidyne Corporation, New Albany, Ind.

The following examples are illustrative of the present invention. Itshould be understood that the examples are not intended to limit theinvention and that various changes may be made by those skilled in theart without changing the essential characteristics and the basic conceptof the invention.

EXAMPLE 1

Mica filled polypropylene sheets (20 mil) and unfilled polypropylenesheets (22 mil) were extruded, as shown in FIG. 1, with conditionsspecified in Table 1. These extrusion process conditions may be variedas necessary to produce sheets which are of acceptable quality.Specifically, the operable temperature ranges for barrel zones 1, 2, and3 are about respectively, 350 to 425° F., 400 to 450° F., and 450 to500° F. The adaptor, feedblock, and die temperatures can all be in aboutthe range of 450 to 500° F. The range of values for extruder driveamperes, extruder speed, melt pressure, die pressure, chill rolltemperature, and line speed are about respectively, 12 to 20 amp., 60 to100 RPM, 1500 to 2500 psi, 450 to 650 psi, 120 to 140° F., and 3 to 8FPM. Sheets were subsequently vacuum thermoformed into plates and othercontainers and lids as set forth in FIGS. 5 through 21. Tables 2 and 3show, respectively, rigidity values and caliper data for the sidewall,bottom, and flange (rim) areas of vacuum formed plates using condition(B) of FIG. 2 and having a dimension of 10.25 or 8.75 inches. In eachtable, individual rigidity values are shown for each specimen. Inaddition, the caliper uniformity for sidewall, bottom, and flange areasare reported for each specimen, along with the summary statistics.Specifically, the caliper of each plate specimen in Tables 2 and 3 wasmeasured ten times using a Fowler gauge for each of the three regions ofinterest consisting of the sidewall, bottom, and flange areas, and theaverage value for each plate specimen is reported along with thecorresponding standard deviation (i.e., individual plate statistics). Inthe case of the three plates of Table 2, the caliper summary statistics(expressed in the average properties row) were obtained on the basis ofaveraging 30 measurements, wherein the standard deviation is reportedfor each of the three regions of interest. In the case of the fiveplates of Table 3, the caliper summary statistics were calculated on thebasis of averaging 50 measurements where again the standard deviation isreported for each of the three regions of interest. Therefore, thecaliper data of Tables 2 and 3 located in the average property rowspertain to global statistics rather than individual plate statistics.The caliper uniformity parameter consists of the coefficient ofvariation (COV) which is calculated as the standard deviation of caliperdivided by the mean caliper, whereas the ratio is multiplied by 100,whereas the above described global averages and associated standarddeviations are employed. A lower COV value is desirable since itsignifies improved caliper uniformity for mica filled polypropyleneplates with respect to unfilled polypropylene plates. Tables 2 and 3show that mica reduces COV of polypropylene from 9.9 to 4.3 in sidewalland from 9.6 to 2.0 in the flange area. Therefore, caliper uniformity insidewall improved by more than a factor of 2 and caliper uniformity inthe flange improved by over a factor of 4. The improvement of caliperuniformity is critical for promoting plate dimensional stability duringfood transport and microwave cooking operations. In great contrast tomica filled polypropylene plates, the unfilled polypropylene platesexhibited poor quality as evidenced by poorly defined rim area, andsharkskin, very rough surface. These data demonstrate that mica greatlyimproves the drawability of polypropylene as evidenced by improvedcaliper uniformity, as well as improved thermoformability, both of whichare due to enhanced melt strength relative to unfilled polypropylene.Mica is the preferred reinforcing mineral filler for enhancing the meltstrength because of its highly regular, high aspect ratio morphologywhich can be thought of as resulting in "inter-particle connectivity" or"physical crosslinking." The significant reinforcing effect of mica isalso evidenced by a SSI plate rigidity value of 671 grams per 0.5 inchesfor PP/mica at a basis weight of about 350 lbs. per 3000 square footream versus 342 grams per 0.5 inches for unfilled PP at a basis weightof about 280 lbs. per 3000 square foot ream.

                  TABLE 1                                                         ______________________________________                                        Sheet Extrusion Conditions for                                                Mica Filled Polypropylene and Unfilled Polypropylene                          CONDITION       PP/MICA  UNFILLED PP                                          ______________________________________                                        Barrel zone 1 (°F.)                                                                    395      395                                                  Barrel zone 2 (°F.)                                                                    425      425                                                  Barrel zone 3 (°F.)                                                                    475      475                                                  Adaptor (°F.)                                                                          470      450                                                  Feed block (°F.)                                                                       470      460                                                  Die zones 1-3 (°F.)                                                                    470      475                                                  Extruder RPM    80       70                                                   Drive amperes   16       19                                                   Melt pressure (psi)                                                                           1700     1780                                                 Die pressure (psi)                                                                            550      825                                                  Line speed (FPM)                                                                              6.1      5.0                                                  Chill roll temp. (°F.)                                                                 130      137                                                  ______________________________________                                    

                  TABLE 2                                                         ______________________________________                                        Caliper and SSI Rigidity Data for 10-1/4 Inch Plates                          Thermoformed From Unfilled Polypropylene Sheet                                Plate    SSI Rigidity                                                                            Sidewall  Bottom  Flange                                   Specimen ID                                                                            (g/0.5 in.)                                                                             Caliper (mil)                                                                           Caliper (mil)                                                                         Caliper (mil)                            ______________________________________                                        72-6     364       18.7 ± 1.9                                                                           20.7 ± 0.8                                                                         22.9 ± 2.8                            (COV) *            10.1      3.9     12.2                                     72-7     382       19.2 ± 2.0                                                                           20.6 ± 0.4                                                                         23.3 ± 0.8                            (COV)              10.4      1.9     3.4                                      72-8     280       19.6 ± 1.9                                                                           20.6 ± 0.5                                                                         23.3 ± 2.8                            (COV)              9.7       2.4     12.0                                     Average  342 ± 54.4                                                                           19.19 ± 1.89                                                                         20.64 ± 0.58                                                                       23.15 ± 2.21                          Properties                                                                    (COV)    15.9      9.85      2.81    9.55                                     ______________________________________                                         * COV = Coefficient of Variation                                         

                  TABLE 3                                                         ______________________________________                                        Caliper and SSI Rigidity Data for 10-1/4 inch Plates                          Thermoformed From Polypropylene/Mica/TiO.sub.2  Sheet                         Plate    SSI Rigidity                                                                            Sidewall  Bottom  Flange Caliper                           Specimen ID                                                                            (g/0.5 in.)                                                                             Caliper (mil)                                                                           Caliper (mil)                                                                         (mil)                                    ______________________________________                                        72-1     705       18.3 ± 1.1                                                                           17.4 ± 0.5                                                                         18.2 ± 1.0                            (COV) *            6.0       2.9     5.5                                      72-2     659       17.0 ± 1.5                                                                           17.9 ± 0.7                                                                         18.4 ± 0.5                            (COV)              8.8       3.9     2.7                                      72-3     654       17.3 ± 1.6                                                                           17.0 ± 0.6                                                                         18.2 ± 0.7                            (COV)              9.2       3.5     3.8                                      72-4     669       16.9 ± 1.2                                                                           16.7 ± 1.1                                                                         18.9 ± 0.8                            (COV)              7.1       6.6     4.2                                      72-5     668       16.3 ± 1.0                                                                           16.3 ± 0.9                                                                         19.0 ± 0.9                            (COV)              6.1       5.5     4.7                                      Average  671 ± 20                                                                              17.3 ± 0.76                                                                         17.1 ± 0.6                                                                          18.5 ± 0.38                          Properties                                                                    (COV)    2.98      4.3       3.5     2.0                                      ______________________________________                                         * COV Coefficient of Variation                                           

EXAMPLE 2

Extruded mica filled polypropylene sheets prepared as described inExample 1 were characterized with respect to surface gloss androughness. Table 4 shows 75 degree gloss and Parker Roughness (airflowmethod) data for an extruded mica filled polypropylene sheet versus sameproperties for the food contact (air) side of vacuum formed 10.25 inchplates produced according to condition (B) of FIG. 2 using the samesheet formulation. The unique thermally induced micronodular surface ischaracterized by significant decrease in gloss and significant increasein roughness as shown in the two photomicrographs in FIG. 22, whichresults in a stoneware or pottery like appearance with aesthetic appeal.The Parker Roughness method has been described in this specificationprior to the Example section.

                  TABLE 4                                                         ______________________________________                                        GLOSS AND ROUGHNESS PROPERTIES OF THE FOOD                                    CONTACT SIDE OF POLYPROPYLENE/MICA/TIO.sub.2                                  PLATE SURFACE VERSUS NEAT EXTRUDED SHEET                                                  GLOSS        PARKER ROUGHNESS                                     SAMPLE ID   (75 DEGREES) *                                                                             (MICRONS)                                            ______________________________________                                        72-1 (Plate)                                                                              22.4         13.41                                                72-2 (Plate)                                                                              30.6         14.05                                                72-3 (Plate)                                                                              24.8         14.89                                                72-4 (Plate)                                                                              24.3         14.24                                                72-5 (Plate)                                                                              24.5         12.48                                                PLATE AVERAGE                                                                             25.3 ± 3.1                                                                              13.8 ± 0.9                                        72-12-1 (Sheet)                                                                           45.7         5.92                                                 72-12-2 (Sheet)                                                                           47.2         7.43                                                 72-12-3 (Sheet)                                                                           --           5.89                                                 72-12-4 (Sheet)                                                                           --           6.35                                                 72-12-5 (Sheet)                                                                           --           5.84                                                 72-12-6 (Sheet)                                                                           --           8.15                                                 SHEET AVERAGE                                                                             46.5          6.6 ± 0.97                                       ______________________________________                                         * = Average of Machine and Cross Machine Directions                      

As shown in Table 4, the food contact side is rougher as evidenced byincreased roughness and decreased gloss relative to the neat extrudedsheet. The rough appearance is desirable for purpose of creating themicronodular surface giving the container and plate a stoneware look.

EXAMPLE 3

Mica filled polypropylene sheets were successfully vacuum thermoformedinto 12 oz. oval microwave containers, whereby the base was producedusing mode (B) of FIG. 2 and the lid was produced using mode (A) of FIG.2. In contrast, attempts to form unfilled polypropylene sheet into thesame container were not successful.

EXAMPLE 4

Sheet rolls (17.5 inch wide), at three calipers were extruded asdescribed in Example 1 and FIG. 1. Table 5 summarizes the PP/40% micamaterial and process conditions. Table 6 summarizes the PP/40% micasheet properties.

                                      TABLE 5                                     __________________________________________________________________________    PP/Mica Extrusion Process Conditions Summary                                     Barrel                                                                            Barrel                                                                            Barrel                                                                Zone 1                                                                            Zone 2                                                                            Zone 3                                                                            Adaptor                                                                           Feed                                                          Temp.                                                                             Temp.                                                                             Temp.                                                                             Temp.                                                                             Block   Die  Die  Die  Screw                               Plate                                                                            (F.)                                                                              (F.)                                                                              (F.)                                                                              (F.)                                                                              Temp.                                                                             Line                                                                              Zone 1                                                                             Zone 2                                                                             Zone 3                                                                             RPM Drive                                                                             Melt                                                                              Die Chill Roll          Size                                                                             Actual/                                                                           Actual/                                                                           Actual/                                                                           Actual/                                                                           Actual/                                                                           Speed                                                                             Temp. (F.)                                                                         Temp. (F.)                                                                         Temp. (F.)                                                                         Actual/                                                                           Am- Pressure                                                                          Pressure                                                                          Temp. (F.)          (in.)                                                                            Set Set Set Set Set (fpm)                                                                             Actual/Set                                                                         Actual/Set                                                                         Actual/Set                                                                         Set peres                                                                             (psi)                                                                             (psi)                                                                             Actual/Set          __________________________________________________________________________    11 395/395                                                                           452/425                                                                           475/475                                                                           470/470                                                                           470/470                                                                           9.27                                                                              470/470                                                                            469/470                                                                            470/470                                                                            125 18.3                                                                              1387                                                                              694 130/130             10 376/375                                                                           410/410                                                                           431/430                                                                           430/430                                                                           430/430                                                                           8.32                                                                              430/430                                                                            430/430                                                                            430/430                                                                            130 19.3                                                                              2012                                                                              737 130/130             9  375/376                                                                           410/410                                                                           434/430                                                                           430/430                                                                           430/430                                                                           8.07                                                                              430/430                                                                            430/430                                                                            430/430                                                                            132 24.2                                                                              2112                                                                              686 130/130             __________________________________________________________________________

                  TABLE 6                                                         ______________________________________                                        PP/Mica Sheet Property Summary                                                Plate Size               Overall Basis Weight-Avg.                            (in.)   Overall Caliper-Avg. (mil)                                                                     (lb./3000 ft.   2)                                   ______________________________________                                        11      18.46 +/- 0.36   308.07 +/- 13.72                                     10      17.20 +/- 0.10   288.80 +/- 9.89                                       9      16.94 +/- 0.10   268.11 +/- 7.50                                      ______________________________________                                    

EXAMPLE 5

Plates from sheet specifications set forth in Example 4 were producedusing 1-up water cooled female molds (with pressure box/vacuumassembly), followed by matched metal punch trimming. Mold temperaturewas 70° F., while sheet temperatures for the 9, 10, and 11 inch plateruns were respectively 300° F., 310° F., and 295° F. The 9 and 10 inchplates were produced at 20 cycles/minute while the bulk of the 11 inchplates were made at 25 cycles/minute.

Oven temperature control on the commercial machine was good due to thecombination of top glass heaters and bottom calrod heaters with properzoning. In general, higher temperatures produce more micronodularity atthe expense of more pronounced sheet sag and wrinkling while lowtemperatures tend to reduce sag at the expense of diminished stonewareappearance.

Best results (i.e., micronodular matte eating surface without "webbing"or wrinkling) were obtained by increasing the top oven temperature by3-5° F. and decreasing the bottom by a corresponding amount. Thisability to selectively control oven temperature in effect facilitateddetermination of the preferred process temperature window of PP/micasheets.

Set forth in Table 7 are the physical properties of plates having theshape set forth in FIGS. 9 through 12 and having a diameter of 9, 10,and 11 inches.

                                      TABLE 7                                     __________________________________________________________________________    Plate Physical Property Data                                                  Product Size      9 inch plate                                                                         10 inch plate                                                                        11 inch plate                                 __________________________________________________________________________    Plates Produced   15,000 10,000 10,000                                        Plate Weight                                                                              Avg.   18.31  24.40  32.02                                        g.          Std. Dev.                                                                            0.27   1.01   0.86                                         Basis Weight                                                                              Avg.  248.28 266.97 288.18                                        #/ream      Std. Dev.                                                                            3.80   9.67   7.09                                         Caliper     Avg.   15.89  16.41  17.32                                        mils        Std. Dev.                                                                            0.48   0.49   0.86                                         Dry Rigidity                                                                              MD Avg.                                                                             300.2  341.6  411.9                                         gms/0.5 inches                                                                            Std. Dev.                                                                           56.0   56.0   30.0                                          Dry Rigidity                                                                              CD Avg.                                                                             307.5  345.9  417.4                                         gms/0.5 inches                                                                            Std. Dev.                                                                           57.0   50.0   29.0                                          Dry Rigidity                                                                              GM Avg.                                                                             303.4  343.4  414.4                                         gms/0.5 inches                                                                            Std. Dev.                                                                           54.0   52.0   26.0                                          Gloss       60°                                                                          3.7 ± 0.6                                                                         3.7 ± 0.6                                                                         5.5 ± 1.2                                              75°                                                                          9.0 ± 1.7                                                                         9.5 ± 2.1                                                                         15.6 ± 3.4                                 Color       L*    80.5 ± 2.8                                                                        81.3 ± 0.9                                                                        80.7 ± 0.3                                 Hunter      a*    0.67 ± 0.007                                                                      0.77 ± 0.07                                                                       1.2 ± 0.1                                              b*     6.3 ± 0.005                                                                       6.2 ± 0.05                                                                       6.7 ± 0.1                                  Whiteness Index                                                                           %     33.5 ± 0.7                                                                        33.9 ± 0.8                                                                        31.1 ± 0.4                                 Parker Print Roughness                                                                    microns                                                                             16.3 ± 1.63                                                                       15.9 ± 1.78                                                                       14.8 ± 1.86                                __________________________________________________________________________

EXAMPLE 6

The sheets and plates were prepared as illustrated in Example 1 andFIGS. 1 and 2. Table 8 shows sheet extrusion and forming conditions.Table 9 contains formulation composition information. Table 9 shows theplate physical test results. FIGS. 23 and 24 show respectively, glossand plate rigidity versus mica level (at constant mica/TiO₂ ratio).

                  TABLE 8                                                         ______________________________________                                        Extrusion/Forming Conditions                                                  ______________________________________                                        Barrel Zone 1   375°F.                                                 Barrel Zone 2   410°F.                                                 Barrel Zone 3   430°F.                                                 Adaptor         430°F.                                                 Feedblock       430°F.                                                 Die Zones 1/2/3 430°F.                                                 RPM             130                                                           Chill Roll      130°F.                                                 Target Sheet Caliper                                                                          18.3 mil                                                      Sheet Width     18.0 inches                                                   Comet Former Top Heater                                                                       20%                                                           Comet Former Bottom Heater                                                                    35%                                                           Comet Former Time                                                                             50-60 seconds                                                 Plate Design    11 inch                                                                       (having shape set forth in FIGS. 9-12)                        ______________________________________                                    

                                      TABLE 9                                     __________________________________________________________________________    Physical Test Properties                                                      __________________________________________________________________________    Run                                                                              Plate Weight                                                                         Basis Weight                                                                          Caliper                                                                              Dry Rigidity - MD                                                                      Dry Rigidity - CD                                                                     Dry Rigidity - GM                   No.                                                                              (g)    (#/ream)                                                                              (mil)  (gm/0.5 in)                                                                            (gm/0.5 in)                                                                           (gm/0.5 in)                                                                            Mica (Wt                                                                            TiO.sub.2 (Wt        __________________________________________________________________________                                                             %)                   1  33.52 ± 0.17                                                                      294.92 ± 2.24                                                                      16.91 ± 0.08                                                                      543.0 ± 12.0                                                                        543.4 ± 11.7                                                                       543.2 ± 11.6                                                                        40    2.5                  2  30.10 ± 0.39                                                                      259.13 ± 5.04                                                                      16.12 ± 0.26                                                                      363.6 ± 15.3                                                                        363.2 ± 16.2                                                                       363.4 ± 15.4                                                                        40    2.5                  3  31.20 ± 0.17                                                                      271.34 ± 2.24                                                                      16.26 ± 0.08                                                                      468.4 ± 14.4                                                                        464.8 ± 16.5                                                                       466.6 ± 15.4                                                                        40    0                    4  32.81 ± 0.69                                                                      288.66 ± 8.48                                                                      17.40 ± 0.31                                                                      480.4 ± 38.2                                                                        482.0 ± 37.6                                                                       481.2 ± 37.9                                                                        30    1.88                 5  29.47 ± 0.09                                                                      254.82 ± 3.77                                                                      17.26 ± 0.32                                                                      338.4 ± 8.6                                                                         339.6 ± 12.2                                                                       339.0 ± 9.7                                                                         20    1.25                 6  30.17 ± 0.30                                                                      263.73 ± 2.20                                                                      17.32 ± 0.32                                                                      334.7 ± 9.1                                                                         326.3 ± 5.0                                                                        330.5 ± 6.8                                                                         25    1.56                 7  36.02 ± 1.00                                                                       313.87 ± 10.98                                                                    18.26 ± 0.52                                                                      473.3 ± 48.4                                                                        479.7 ± 59.7                                                                       476.5 ± 54.0                                                                        40    2.5                  8  33.15 ± 0.37                                                                      289.62 ± 2.49                                                                      17.39 ± 0.34                                                                      440.3 ± 4.0                                                                         428.0 ± 10.4                                                                       434.1 ± 4.6                                                                         40    2.5                  9  34.74 ± 0.50                                                                      305.79 ± 2.51                                                                      17.69 ± 0.24                                                                      440.3 ± 18.6                                                                        449.3 ± 11.0                                                                       444.8 ± 14.6                                                                        40    1.75                 10 33.24 ± 0.20                                                                      291.79 ± 3.18                                                                      17.07 ± 0.20                                                                      407.3 ± 4.0                                                                         409.0 ± 8.5                                                                        408.2 ± 5.2                                                                         40    1.75                 11 36.07 ± 0.30                                                                      316.39 ± 2.09                                                                      18.15 ± 0.11                                                                      501.0 ± 17.3                                                                        489.7 ± 8.5                                                                        495.3 ± 12.3                                                                        40    1.0                  12 33.84 ± 0.55                                                                      293.84 ± 4.37                                                                      17.70 ± 0.28                                                                      413.0 ± 18.0                                                                        402.3 ± 19.7                                                                       407.6 ± 18.6                                                                        40    1.0                  13 31.00 ± 0.38                                                                      271.53 ± 5.09                                                                      17.81 ± 0.32                                                                      413.7 ± 45.1                                                                        405.3 ± 44.4                                                                       409.4 ± 44.2                                                                          27.5                                                                              1.72                 14 31.77  265.64  17.37 ± 0.80                                                                      384.0    372.0   378.0    25    1.56                 15 31.02  269.00  17.41 ± 0.01                                                                      335.0    364.0   359.5    30    1.87                 16 30.09  256.85  16.87 ± 0.57                                                                      325.0    328.0   326.5    30    1.87                 17 30.36  261.41  16.70 ± 0.17                                                                      334.0    346.0   339.9    30    1.87                 __________________________________________________________________________    Run                                                  Parker Print             No. Gloss 60°                                                                    Gloss 75°                                                                    Color Hunter L*                                                                       Color Hunter A*                                                                        Color Hunter B*                                                                        Whiteness Index                                                                          Roughness                __________________________________________________________________________                                                         (micron)                 1   4.5 ± 0.3                                                                        11.2 ± 1.0                                                                       78.29 ± 0.5                                                                        0.99 ± 0.14                                                                         7.13 ± 0.14                                                                         26.72 ± 0.36                                                                          15.44 ± 3.19          2   4.8 ± 0.4                                                                        14.9 ± 0.3                                                                       80.99 ± 0.2                                                                        0.70 ± 0.04                                                                         6.40 ± 0.02                                                                         32.62 ± 0.18                                                                          15.28 ± 2.08          3   4.3 ± 0.3                                                                        11.8 ± 1.0                                                                       52.45 ± 0.5                                                                        3.17 ± 0.14                                                                         14.77 ± 0.14                                                                        -6.65 ± 0.36                                                                          13.86 ± 1.68          4   5.4 ± 0.5                                                                        16.0 ± 4.5                                                                       78.85 ± 0.1                                                                        0.93 ± 0.06                                                                         7.41 ± 0.05                                                                         26.34 ± 0.19                                                                          15.01 ± 1.81          5   7.3 ± 0.1                                                                        24.3 ± 0.3                                                                       78.83 ± 0.1                                                                        1.33 ± 0.05                                                                         8.10 ± 0.03                                                                         23.75 ± 0.16                                                                          13.62 ± 0.13          6   5.9 ± 0.1                                                                        18.3 ± 0.3                                                                       78.32 ± 0.1                                                                        0.83 ± 0.03                                                                         7.55 ± 0.03                                                                         25.26 ± 0.13                                                                          15.67 ± 2.17          7   4.4 ± 0.1                                                                        11.6 ± 0.5                                                                       81.04 ± 0.4                                                                        0.91 ± 0.03                                                                         7.29 ± 0.07                                                                         28.55 ± 0.88                                                                          16.07 ± 0.93          8   4.2 ± 0.1                                                                        11.7 ± 0.5                                                                       75.30 ± 0.8                                                                        1.22 ± 0.10                                                                         8.36 ± 0.17                                                                         19.05 ± 0.72                                                                          14.86 ± 1.40          9   4.4 ± 0.2                                                                        11.9 ± 0.4                                                                       76.77 ± 0.4                                                                        1.02 ± 0.04                                                                         8.19 ± 0.06                                                                         21.21 ± 0.51                                                                          14.91 ± 1.83          10  4.1 ± 0.1                                                                        11.5 ± 0.3                                                                       72.74 ± 0.4                                                                        1.31 ± 0.10                                                                         9.17 ± 0.10                                                                         14.49 ± 0.49                                                                          15.15 ± 0.50          11  4.0 ± 0.1                                                                        11.3 ± 0.3                                                                        70.35 ± 0.20                                                                      1.43 ± 0.04                                                                         9.62 ± 0.09                                                                         11.25 ± 0.38                                                                          16.12 ± 1.76          12  4.4 ± 0                                                                          13.2 ± 0.4                                                                        68.70 ± 0.62                                                                      1.62 ± 0.09                                                                         9.72 ± 0.11                                                                          9.83 ± 0.72                                                                          14.93 ± 1.14          13  5.0 ± 0.1                                                                        15.0 ± 0.7                                                                        78.87 ± 0.12                                                                      0.64 ± 0.03                                                                         7.40 ± 0.03                                                                         26.40 ± 0.16                                                                          15.90 ± 1.41          14  6.7 ± 0.2                                                                        20.9 ± 0.7                                                                        78.95 ± 0.03                                                                      0.89 ± 0.04                                                                         6.78 ± 0.01                                                                         28.76 ± 0.55                                                                          15.75 ± 1.74          15  6.1 ± 0.1                                                                        19.0 ± 0.6                                                                        79.38 ± 0.03                                                                      0.92 ± 0.03                                                                         6.81 ± 0.01                                                                         28.83 ± 1.15                                                                          13.97 ± 0.33          16  5.6 ± 0.2                                                                        18.9 ± 0.6                                                                        71.22 ± 0.08                                                                      -10.47 ± 0.08                                                                       -6.36 ± 0.06                                                                        64.16 ± 0.61                                                                          --                       17  6.0 ± 0.1                                                                        20.5 ± 0.5                                                                        55.98 ± 0.04                                                                      -11.16 ± 0.03                                                                       -28.54 ± 0.07                                                                       16.70 ± 0.17                                                                          16.09                    __________________________________________________________________________                                                         ± 2.19            

EXAMPLE 7

Table 10 shows the sheet process conditions employed for a commercialsheet extrusion run of several mica filled polypropylene formulations.These sheets suitably have a basis weight of about 200 to 950, per 3000square foot ream, preferably about 200 to 400 per 3000 square foot ream.These mica filled polypropylene sheets had a mica content in the rangeof 25 to 35 weight percent.

The extrusion of coupled mica and polypropylene blends was conducted ona 6" commercial extruder line. The extruder was an Egan 24/1 UD with ageneral purpose screw. The die was an Extrusion Die Inc. 52" coat hangertype. The stack conditioning rolls were top polished chrome, middlematte (40 RA surface), and bottom polished chrome. Extrusion conditionsare set forth in Table 10. The matte chill roll assisted with theformation of the micronodular surface during thermoforming of the sheetwith beneficially improving breadth of forming temperature window incontrast with non matted smooth sheets of prior art depicted in FIG. 26.

                                      TABLE 10                                    __________________________________________________________________________    Sheet Extrusion Run Conditions For Mica Filled Polypropylene                              Run Point     Set Point                                                       PP/25% wt                                                                           PP/30% wt                                                                             PP/25% wt                                                                           PP/30% wt                                                 Mica  Mica    Mica  Mica                                          __________________________________________________________________________    Barrel Zone 1 Temp (F.)                                                                   352   350     350   350                                           Barrel Zone 2 Temp (F.)                                                                   385   375     375   375                                           Barrel Zone 3 Temp (F.)                                                                   404   400     400   400                                           Barrel Zone 4 Temp (F.)                                                                   422   421     420   420                                           Barrel Zone 5 Temp (F.)                                                                   435   430     430   430                                           Adaptor Temperature (F.)                                                                  431   430     430   430                                           Melt Temperature (F.)                                                                     485   482     --    --                                            Die Zone 1 Temp (F.)                                                                      430   430     430   430                                           Die Zone 2 Temp (F.)                                                                      430   430     430   430                                           Die Zone 3 Temp (F.)                                                                      431   430     430   430                                           Die Zone 4 Temp (F.)                                                                      431   430     430   430                                           Die Zone 5 Temp (F.)                                                                      430   430     430   430                                           Screw RPM   55    54                                                          Drive Amperes                                                                             --    432                                                         Melt Pressure (psi)                                                                       1704  1705-1760*                                                  Top Roll Temp (F.)                                                                        132   133                                                         Middle Roll Temp (F.)                                                                     97    98                                                          Line Speed (fpm)                                                                          42    37                                                          Roll Gap top (mil)                                                                        17    17                                                          Roll Gap Bottom (mil)                                                                     21    21                                                          Die Gap (mil)                                                                             --    19-side of die,                                                               13-middle of die                                            Die-Full Width (in)                                                                       52    52                                                          Die to Roll Distance (in)                                                                 ˜6.0                                                                          4.5                                                         Full Sheet Width (in)                                                                     50.5  51.5                                                        Trim Width (each side) (in)                                                               1.75  1.75                                                        Final Split Roll Width (in)                                                               16    16                                                          Screen Pack 20 mesh                                                                             20 mesh                                                     Throughput (lb./hr.)                                                                      --    924                                                         Back Pressure (psi)                                                                       1830  1830                                                        Sheet Caliper (mil)                                                                       --    17.3                                                        Roll Weight (lb.)                                                                         400   430                                                         Roll Diameter (in)                                                                        45    40                                                          Roll Footage (ft)                                                                         --    6,240                                                       __________________________________________________________________________     *No screen pack change                                                   

The sheets produced with conditions set forth in Table 10 were mattefinished. The photomicrographs of the sheets produced according to theprocess of Table 10 as contrasted to those produced under conditionssimilar to Example 1 are set forth in photomicrographs of FIGS. 25 and26.

                  TABLE 11                                                        ______________________________________                                        Roughness and Gloss Properties of                                             PP/30% Mica Extruded Sheets and Thermoformed Plates                                  Sheet Thermoforming                                                                         Parker Roughness                                         Surface                                                                              Temperature (°F.)                                                                    (microns)    Gloss (75°)                          ______________________________________                                        A      --             8.56 ± 0.39                                                                            4.99 ± 0.11                              B      --            15.82 ± 0.74                                                                            8.05 ± 0.30                              C      305           13.14 ± 0.74                                                                            14.3 ± 1.0                               D      300           11.74 ± 0.86                                                                            11.6 ± 1.0                               E      292           12.10 ± 0.82                                                                            11.7 ± 1.0                               F      265           10.63 ± 0.68                                                                            8.20 ± 0.6                               G      --            6.17         82.10                                       H      --            5.14         80.75                                       ______________________________________                                         (A) Matte extruded sheet having top matte side.                               (B) Extruded sheet (A)bottom side opposite to matte side                      (C, D, E, F) Plateeating side corresponding to top matte side of (A)          (G) Nonmatte extruded sheettop side (no matte roll)                           (H) Nonmatte extruded sheetbottom side (no matte roll)                   

For a non-matte extruded sheet, usually plate gloss and plate roughnessare inversely related (e.g., high gloss corresponds to low roughness andvice versa as demonstrated in prior art data generally obtained). Inthat case, achieving desirable micronodular texture is within atemperature range (about 295° F. to 305° F.) where above this range theforming process is sag limited while below this range the plate exhibitspoor micronodular character as manifested by high gloss and lowroughness.

The use of a matte roll in the chill roll stack portion of the extrusionprocess effectively broadens the commercially attractive thermoformingprocess temperature range (about 265° F. to 305° F.). Specifically,plates having acceptable surface micronodularity can be formed at lowertemperatures, whereby the decrease in plate roughness is compensated byan unexpected decrease in plate gloss using sheet surface (A). Thisbeneficial increase in plate forming temperature window from about 10°F. to about 40° F. is brought about by imparting a matte surface finishto the extruded sheet.

Thermoforming is the pressing or squeezing of pliable material intofinal shape. In the simplest form, thermoforming is draping of asoftened sheet over a shaped mold. In the more advanced form,thermoforming is automatic, high speed positioning of a sheet having anaccurately controlled temperature into a pneumatically actuated formingstation.

The extruded sheet used in the suitable forming and thermoformingprocess, or the preferred thermoforming process as shown in FIG. 2 has athickness of about 0.010 to 0.080 inches, suitably 0.010 to 0.030inches, and preferably 0.015 to 0.025 inches. Suitable mica fillerloading level in the extruded sheet is in the range of 25-30 weightpercent, whereby mica flake aspect ratio is in the range of 30-300, morepreferably 80-120, with particle size range of about 50 to 500 microns.

By matte finishing one side of the sheet using matte roll, thecommercial thermoforming was suitably conducted at a broader temperaturewindow of about 265° F. to 305° F. while without matte finishing, thethermoforming using the same commercial equipment was conducted at atemperature of about 295° F. to 305° F.

The runs on commercial equipment using PP/30% mica and PP/25% micaformulations showed that the thermoforming temperature window range hasbeen expanded from about 10° F. (previous trial) to as high as about 35°F. This is primarily due to the fact that we beneficially used a matteroll in the chill roll stack during the extrusion process. This gave asmooth matte finish for the air side of the sheet (i.e., plate eatingsurface) while the rougher bottom side was in contact with thesandblasted mold side during the forming process. Use of matte sheet inturn enabled forming at lower temperatures (which is good for sagavoidance) without much loss in micronodularity. Specifically, theforming window was in the range of 265° F. to about 300° F. to 305° F.where best balance of process stability and product appearance/texturewas seen at about 280° F. to 290° F.

EXAMPLE 8

FIG. 3 shows rigidity versus current plate material cost comparisons formica filled polypropylene plates versus competitor plastic disposableplates. "J" refers to mica filled polypropylene plate of this inventionand "S" refers to polystyrene based plates such as those currentlymanufactured by Solo Cup Company. Average plate calipers are indicatedfor each plate type and size. The left side of the diagram shows datafor 8.75 inch plates whereby the J plate rigidity is about three timeshigher than S at significantly reduced caliper and cost. The right sideof the diagram shows data for 10.25 inch plates whereby J plate rigidityis more than seven times higher than S at the same caliper. The opencircle point corresponds to an estimated rigidity for the 10.25 inch Jplate that is scaled down in caliper so that plate material costs areequivalent to S.

The scaled J caliper X is calculated as X=(19 mil)(2.9 cents/3.8 cents).The theoretical rigidity R1 at equivalent cost for the downscaledcaliper is calculated as:

    (R1/R2)=(14.5 mil/19 mil) exp N

where R2 is the experimental rigidity at 19 mil and N=1.816 is thecaliper exponent value for the Dixie Superstrong 10.25 inch plate designwhich is obtained from the general equation for rigidity:

    R=(KE) TexpN

where E is Young's modulus, K is a shape constant, and T is caliper. Thedata set forth in FIG. 3 demonstrate that the rigidity of the J plate ofthis invention is significantly higher at equivalent or lower materialcost than commercial polystyrene polymer based plates.

EXAMPLE 9

In FIG. 4, the heat resistance performance for mica filled polypropylene10.25 in plates (J), having an average caliper of 19 mil (J) is comparedwith (S) polystyrene based plates (S) of the same size and caliper. Ameasure of heat resistance is dynamic flexural storage modulus E', asmeasured with the Rheometrics Solids analyzer at 10 rad/sec. Higher E'values indicate increased stiffness and improved dimensional stability.Dynamic mechanical spectroscopy is a common technique used forevaluation of viscoelastic properties of polymeric materials withrespect to temperature and input frequency (deformation time scale).Dynamic mechanical properties of flat rectangular specimens of S platematerial and PP/mica sheet of this invention were subjected to flexuraldeformation at 10 rad/sec, using the Rheometrics Solids Analyzer RSAIIinstrument, manufactured by Rheometric Scientific, and equipped with adual cantilever bending fixture. Temperature scans were conducted at0.05% strain using 2° C. temperature steps with a 0.5 minute soak timeat each temperature. From the time lag between input strain delivered bythe driver motor and the stress output measured by the transducer,values of material complex modulus E* are obtained. The parameter E* isformally expressed as E*=E'+iE", where E' is the storage modulus (purelyelastic term) and E" is the loss modulus (purely viscous term). Thestorage modulus E' is defined as the stress in phase with the straindivided by the strain, which gives a measure of the energy stored andrecovered per cycle. The loss modulus E" is defined as the stress 90degrees out of phase with the strain divided by the strain, which givesa measure of the energy dissipated per cycle. The ratio of loss modulusto storage modulus is commonly known as the damping (tan delta) wheredelta is the phase angle between stress and strain. The dynamic storageflexural modulus E' is the operative measure of heat resistanceperformance, where higher values mean higher performance. At ambientconditions (77° F.), E' for mica filled polypropylene plates of thisinvention is appreciably higher than for S. At 250° F., whichcorresponds to aggressive temperatures which are commonly encountered inthe microwave heating or cooking of greasy foods, the heat resistance ofJ plates of this invention is significantly superior to the platesmanufactured by S.

The superior heat resistance of the plates of this invention J versusthe plates sold by S as characterized by E' strongly correlates withactual microwave cook test results for the two plates, as shown in Table12. The S plate warps and loses dimensional stability with many types offoods as well as undergoes undesirable changes when coming in contactwith food as evidenced by some staining and sticking. On the other hand,the J plate of this invention is a superior plate since it has excellentdimensional stability as well as excellent heat resistance when food iscooked and/or reconstituted on it.

                  TABLE 12                                                        ______________________________________                                        MICROWAVE COOKING TEST RESULTS FOR PLATES J AND S                                     PLATE TYPE                                                            FOOD TYPE J               S                                                   ______________________________________                                        donut     pass            sugar glazing sticks                                broccoli/cheese                                                                         pass            significantly deforms                               pepperoni pizza                                                                         pass            moderate deformation,                                                         staining                                            barbecue pork                                                                           slight stain    significant stain/warpage                           pancake/syrup                                                                           pass            significant warpage                                 beans & pork                                                                            pass            significant warpage                                 butter    slight warpage  significant warpage                                 bacon     moderate warpage,                                                                             significant warpage,                                          localized melting, no leak                                                                    rubbery plate flows and                                                       sticks to glass tray                                ______________________________________                                    

Fort James Corporation (J) plate specimens of this invention and platesmanufactured by Solo Cup Company (S) were tested in the microwave(Samsung model MW 8690) with a variety of foods. The highest powersetting (10) was used in all cases and cooking/heating times andprocedures corresponded food manufacturer instructions on the packages.Most tested foods were of the frozen microwaveable type and were placedin a semi-thawed state directly on plates prior to cooking. Whenappropriate, a loose covering of wax paper was employed during thecooking process. After cooking, the plates were gently washed with warmwater and inspected. The following are the detailed test results whichare also summarized in Table 12.

TEST #1 RESULTS--Sugar Glazed Donut

J A large, oval shaped sugar glazed plain donut was microwaved on theplate of this invention for 60 seconds. The sugar glazing melted,bubbled, and flowed on the plate. The boiling sugar and grease mixturecaused the bottom of the plate to feel very warm but the plate exhibitedno warping, no straining, no softening, and no soak-through. The platewas cool enough to be safely handled. The residue of the donut waseasily washed off and the appearance of the used plate was excellent.

S The bottom of the plate got hot and slightly deformed with nosoak-through, however, sugar stuck to the plate.

TEST #2 RESULTS--Broccoli With Cheese Sauce

J Green Giant 10 oz. broccoli with cheese sauce was removed from theflexible pouch and heated for five minutes in the microwave on the platewith loose covering of wax paper. The cheese melted and bubbled on theplate without sticking. The plate bottom was warm, but no soak-throughand no loss of dimensional stability was observed. After washing, nostaining was observed and the appearance of the used plate wasexcellent.

S The plate bottom got hot and significantly deformed with nosoak-through.

TEST #3 RESULTS--Pepperoni pizza

J Tombstone 7 oz. Pepperoni pizza was cooked on an uncovered plate for 4minutes. The cheese melted and started bubbling about halfway throughthe test. The molten cheese mingled with the hot liquid fat exuded fromthe pepperoni and dripped on the sides of the crust onto the plate. Nosticking, no soak-through, no staining, and no loss in plate dimensionalstability was observed and the appearance of the used plate wasexcellent.

S The plate bottom got hot and moderately deformed with no soak-through.The greasy reddish stain from oil in pepperoni could not be completelywashed off.

TEST #4 RESULTS--Microwave Kid Meal:

Pork Rib Patties, Barbecue Sauce, Fries, Honey Corn Bread

J A quick meal preparation simulation test was conducted using a Swanson7.2 oz. microwave kids' meal with ingredients consisting of partiallycooked boneless pork rib patties, barbecue sauce, fries, and honey cornbread. The food was transferred from the compartmented tray onto theplate. Sauce was spooned on top of the pork meat and was allowed to dripon the sides of the patties and onto the plate. The cornbread batter wasspooned out and was placed on the plate next to the fries. The food wasloosely covered with wax paper and cooked for 3.5 minutes. Examinationafter microwaving showed that the cornbread was fully cooked and therewas no sticking or damage to the plate. The fries and pork meat withsauce caused no soak-through and no loss in plate dimensional stability.Washing of plate revealed the presence of slight staining from barbecuesauce. Overall, the appearance of the used plate was very good.

S The plate bottom deformed mainly from pork meat with considerablestaining from the barbecue sauce without soak-through.

TEST #5 RESULTS--Beans with Pork and Tomato Sauce

J Beans with pork and tomato sauce (8 oz can) were placed on the plate,covered with wax paper and heated for 2 minutes to near boiling. Thebottom of plate got hot, but the rim was cool to touch. The hot platebottom exhibited no bulging and also, when the hot food plate washandled by the rim there was no perceived loss in dimensional stability.No soak-through, no warping, and no staining was observed. Theappearance of the plate was excellent.

S The plate bottom became very hot and severely deformed with nosoak-through and when handled by the rim, the plate felt like it had lowrigidity.

TEST #6 RESULTS--Pancakes with Syrup and Precooked Bacon

J In this test, Swanson microwave pancakes and bacon breakfast (4.5 oz.size) were used. The semi-thawed meal consisted of three pancakes andthree partially precooked bacon strips. The pancakes and bacon wereremoved from the tray in carton and placed on plate. Approximately 5teaspoons of pancake syrup was spooned over the pancakes and theassembled meal was covered with wax paper and microwaved for 2 minutes.Although the bottom of the plate got hot, the overall plate performancewas excellent, i.e. no warpage, no soak-through, no loss in dimensionalstability, and no staining. Some hot grease was exuded by the baconduring crisping but there was no observed damage to the plate. Theappearance of the used plate was excellent.

S The plate bottom became hot and significantly deformed (especially inareas where bacon was placed), but no soak-through was observed and whenhandled by the rim, the plate felt soft.

TEST #7 RESULTS--Butter

J Butter (5 tsp. chunk) was placed the on plate and was loosely coveredwith wax paper and was microwaved for 3 minutes. The butter meltedcompletely and covered the whole plate bottom. The butter began boilingtoward the end of the test. The plate bottom got very hot and becameslightly warped but no soak-through. The rim of the plate felt cool totouch enabling safe removal of the plate from the microwave oven. Asmall portion of the butter became charred but was easily washed off theplate. Overall plate performance was good.

S The plate bottom became very hot and was significantly warped but nosoak-through was observed and the greasy film residue could not bewashed off completely. Plate felt soft and rubbery when handled by therim.

TEST #8 RESULTS--Bacon

J Three strips of raw, cured bacon were wrapped in three sheets of papertowel and cooked for 5 min. All of the bacon became crispy and about 20%of it was charred. The bottom of plate got very hot but most of rim areawas relatively cool to touch. Grease exuded from bacon and soakedthrough the towel. The grease pooled on the plate bottom, side and onsome rim areas. The grease which pooled in some rim regions causedlocalized melting of the plate but no holes were formed. The hot greasewhich pooled on plate bottom caused significant warpage but nosoak-through. Overall plate performance for Test #8 was lesssatisfactory than Test #7.

S When the raw bacon was wrapped in paper toweling and cooked on the Splate, the bottom became very soft and stuck to the glass tray in themicrowave. Under such hot grease conditions, the adhering polymerregions underwent localized melting and stretched when the plate waslifted off the glass tray. The plate was severely warped but no holesformed and no soak-through was noticed.

With the possible exception of raw bacon, the behavior of the J plate ofthis invention in the microwave oven is considered excellent with avariety of aqueous, greasy/fatty, sugary food combinations. No unusualor off odors were detected during and after cooking for each type offood directly on the plate. The foregoing data demonstrates the superiorproperties of the plates of this invention.

We claim:
 1. A microwaveable, food contact compatible, disposable, rigidand strong container comprising an extruded sheet consisting essentiallyof an admixture of a polyolefin selected from the group consisting ofpolypropylene and polypropylene polyethylene copolymer or a blend, andmixtures of these, mica, and pigment thermoformed by application ofvacuum into the shape of a container; said container furtherexhibiting:(a) a micronodular surface on at least one side of thecontainer surface; and (b) a melting point of no less than about 250°F.;said container being dimensionally stable and resistant to grease,sugar, and water at temperatures up to about 220° F. and of sufficienttoughness to be resistant to cutting by serrated polystyrene flatware.2. The container of claim 1 wherein the polypropylene in the sheet isisotactic polypropylene homopolymer having a melt flow rate of about 0.1to about 5.0.
 3. The container of claim 1 wherein the extruded sheetfurther comprises a coupling agent for promoting adherence between thepolyolefin and the mica, the coupling agent comprising maleic anhydridemodified polypropylene or acrylic modified polypropylene in aconcentration of about 0.5 to about 3 weight percent based on the totalweight of the container.
 4. The container of claim 1 wherein the pigmentis titanium dioxide.
 5. The container of claim 1 wherein the pigment iscarbon black.
 6. The container of claim 1 wherein the container exhibitsa melting point of about 250 to about 330° F.
 7. The container of claim2 wherein the polypropylene moiety or propylene-ethylene copolymer orblend comprises about 40 to 90 percent by weight, the mica comprisesabout 7 to 59 percent by weight, and the pigment comprises about 0.5 to8 percent by weight.
 8. The container of claim 7 wherein the pigmentcomprises about 2.5 to 6.5 percent by weight.
 9. The container of claim7 wherein the mica content comprises about 20 to 35 weight percent. 10.The container of claim 1 in the form of a cup.
 11. The container ofclaim 1 in the form of a bowl.
 12. The container of claim 1 in the formof a tray.
 13. The container of claim 1 in the form of a bucket.
 14. Thecontainer of claim 1 in the form of a souffle dish.
 15. Themicrowaveable container of claim 1 wherein the polyolefin component ofthe extruded sheet is a propylene-ethylene copolymer or blend whereinthe ethylene moiety comprises less than 10 mole percent of the totalcopolymer.
 16. A microwaveable, food contact compatible, disposable,rigid and strong container comprising an extruded sheet consistingessentially of an admixture of a polyolefin selected from the groupconsisting of polypropylene, polypropylene polyethylene copolymer orblend, and mixtures of these and platy inorganic mineral thermoformed byapplication of vacuum into the shape of a container; said containerexhibiting:(a) a micronodular surface on at least one side; and (b) amelting point of no less than about 250° F.; and (c) a basis weight ofat least 130 lbs. per 3000 square foot ream;said container beingdimensionally stable and resistant to grease, sugar, and water attemperatures up to at least 220° F. and of sufficient toughness to beresistant to cutting by serrated polystyrene flatware.
 17. Amicrowaveable, food contact compatible, disposable, rigid and strongcontainer comprising an extruded sheet consisting essentially of anadmixture of a polyolefin selected from the group consisting ofpolypropylene, polypropylene polyethylene copolymer or blend, andmixtures of these, mica, and pigment, formed or thermoformed into theshape of a container; said exhibiting:(a) a basis weight of at least 130pounds per 3000 square foot ream; and (b) a melting point of no lessthan about 250° F.;said container being dimensionally stable andresistant to grease, sugar, and water at temperatures up to at least220° F. and of sufficient toughness to be resistant to cutting byserrated polystyrene flatware.
 18. The container of claim 17 wherein themica content is about 20 to 40 weight percent.
 19. A microwaveable, foodcontact compatible, disposable, rigid and strong container comprising anextruded sheet consisting essentially of a polypropylene orpolypropylene polyethylene copolymer or blend, and mixtures of these andmica, thermoformed by application of vacuum into the shape of acontainer; said container exhibiting:(a) a micronodular surface on atleast one side; and (b) a melting point of no less than about 250° F.;and (c) a basis weight of at least 130 lbs. per 3000 square footream;said container being dimensionally stable and resistant to grease,sugar, and water at temperatures up to at least 220° F. and ofsufficient toughness to be resistant to cutting by serrated polystyreneflatware.
 20. A microwaveable, food contact compatible, disposable,rigid and strong tray comprising an extruded sheet consistingessentially of an admixture of a polyolefin selected from the groupconsisting of polypropylene, polypropylene polyethylene copolymer orblend, and mixtures of these, mica, and pigment, formed or thermoformedinto the shape of a tray; said tray exhibiting:(a) a basis weight of atleast 130 pounds per 3000 square foot ream; and (b) a melting point ofno less than about 250° F.;said tray being dimensionally stable andresistant to grease, sugar, and water at temperatures up to at least220° F. and of sufficient toughness to be resistant to cutting byserrated polystyrene flatware.
 21. A microwaveable, food contactcompatible, disposable, rigid and strong bowl comprising an extrudedsheet consisting essentially of an admixture of a polyolefin selectedfrom the group consisting of polypropylene, polypropylene polyethylenecopolymer or blend, and mixtures of these, mica, and pigment formed orthermoformed into the shape of a bowl; said bowl exhibiting:(a) amicronodular surface on at least one side; and (b) a melting point of noless than about 250° F.;said bowl being dimensionally stable andresistant to grease, sugar, and water at temperatures up to about 220°F. and of sufficient toughness to be resistant to cutting by serratedpolystyrene flatware.
 22. A microwaveable, food contact compatible,disposable, rigid and strong plate comprising an extruded sheetconsisting of an admixture of a polypropylene or polypropylenepolyethylene copolymer or blend, mica, and pigment, formed, thermofothermoformed by application of vacuum into the shape of a plate; saidplate exhibiting:(a) a micronodular surface on at least one side; (b) amelting point of no less than about 250° F.; and (c) thicknessuniformity characterized by a thickness coefficient variation of lessthan five percent; said plate being dimensionally stable and resistantto grease, sugar, and water at temperatures up to at least 220° F. andof sufficient toughness to be resistant to cutting by serratedpolystyrene flat ware.
 23. The plate of claim 22 having a diameter inthe range of about 8.75 inches to 11 inches.
 24. The plate of claim 22having a diameter of 10.25 inches.
 25. The plate of claim 22 wherein thecoupling agent comprises maleic anhydride or acrylic modifiedpolypropylene.
 26. The plate of claim 22 wherein the pigment is titaniumdioxide.
 27. The plate of claim 22 wherein the pigment is carbon black.28. The plate of claim 22 wherein the plate exhibits a melting point ofabout 250 to about 330° F.
 29. The plate of claim 22 wherein thepolypropylene moiety comprises about 40 to 90 percent by weight, themica comprises about 7 to 59 percent by weight, and the pigmentcomprises about 0.5 to 8 percent by weight.
 30. The plate of claim 22wherein the mica comprises about 20 to 40 weight percent and the pigmentcomprises 2.5 to 6.5 weight percent.
 31. The plate of claim 30 whereinat a basis weight of at least 175 pounds per 3000 square foot ream, theplate exhibits a rigidity of at least 400 grams per 0.5 inch whenmeasured by a Single Service Institute Rigidity Tester.
 32. The plate ofclaim 31 wherein at the basis weight of at least about 280 pounds per3000 square foot ream, the plate exhibits a rigidity of at least 400grams per 0.5 inch when measured by a Single Service Institute RigidityTester.
 33. The plate of claim 22 having a rim and having a calipercoefficient of variation in the rim of less than
 5. 34. The plate ofclaim 23 or claim 24 having a rigidity value of at least 250 grams per0.5 inches at a basis weight of 170 lbs. per 3000 square foot ream whenmeasured by a Single Service Institute Rigidity Tester.
 35. The plate ofclaim 22 having a Parker Roughness of at least about 10 microns.
 36. Theplate of claim 35 having a rim and having a caliper coefficient ofvariation in the rim of less than about
 3. 37. The plate of claim 22having a gloss surface below about 30 gloss units on the side in contactwith food.
 38. The plate of claim 22 shaving a caliper coefficient ofvariation in the sidewall of less than about
 7. 39. The plate of claim38 having a caliper coefficient of variation in the sidewall of lessthan about
 5. 40. A microwaveable, food contact compatible, disposable,rigid and strong container comprising an extruded sheet consistingessentially of an admixture of a polyolefin selected from the groupconsisting of polypropylene, polypropylene polyethylene copolymer orblend, and a mixture of these, mica, and pigment, formed, thermoformed,or thermoformed by application of vacuum into the shape of a container;said container exhibiting:(a) a micronodular surface on at least oneside; and (b) a melting point of no less than 250° F.;said containerbeing dimensionally stable and resistant to grease, sugar, and water attemperatures up to about 220° F. and of sufficient toughness to beresistant to cutting by serrated polystyrene flatware, the containerincluding a base portion and lid portion comprising: I (a) a bottom; (b)an upwardly extending peripheral wall joined to said bottom, saidupwardly extending peripheral wall having an inwardly taperingfrusto-conical base seal area formed therein; and (c) a downwardly andoutwardly extending brim joined to said upwardly extending peripheralwall, said brim having an undercut secondary seal ridge formed therein;and a unitary lid comprising: II (a) a top joined to;(b) a downwardlyextending peripheral wall to; (c) an upwardly extending wall having afrusto-conical lid seal area formed therein, said frusto-conical lidseal area being mateable with the frusto-conical base seal area; (d) adownwardly extending wall having a secondary seal furrow mateable withsaid secondary seal ridge; and (e) resilient lid realignment meanslocated between said secondary seal furrow and said frusto-conical lidseal area for simultaneously urging said frusto-conical base seal areainto close engagement with said frusto-conical lid seal area whileurging said secondary seal ridge into engagement with said secondaryseal furrow.
 41. The container of claim 40 wherein the pigment istitanium dioxide.
 42. The container of claim 40 wherein the pigment iscarbon black.
 43. The container of claim 40 wherein the containerexhibits a melting point of about 250 to about 330° F.
 44. The containerof claim 40 wherein the polyolefin moiety comprises about 40 to 80percent by weight, the mica comprises about 19 to 59 percent by weight,and the pigment comprises about 0.5 to 8 percent by weight and whereinthe container has a basis weight of about 130 pounds to 950 pounds per3000 square foot ream.
 45. The container of claim 44 wherein micacomprises about 20 to 40 percent by weight and the pigment comprises 2.5to 6.5 by weight.
 46. A microwaveable, food contact compatible,disposable, rigid and strong lid comprising an extruded sheet consistingessentially of an admixture of a polyolefin selected from the groupconsisting of polypropylene, polypropylene polyethylene copolymer orblend, or mixtures of these, mica, and pigment, formed, thermoformed, orthermoformed by application of vacuum into the shape of a lid; said lidexhibiting:(a) a micronodular surface on at least one side; and (b) amelting point of no less than about 250° F.;said lid being dimensionallystable and resistant to grease, sugar, and water at temperatures up toabout 220° F.
 47. The lid of claim 46 wherein the micronodular surfaceof the lid is not in contact with the food.
 48. A microwaveable, foodcontact compatible, disposable, rigid and strong extruded sheetconsisting of an admixture of a polyolefin selected from the groupconsisting of polypropylene, polypropylene polyethylene copolymer orblend, and mixtures of these, mica, and pigment thermoformed byapplication of vacuum into the shape of a container; said sheetexhibiting a softening point of no less than about 250° F.; said sheetbeing dimensionally stable and resistant to grease, sugar, and water attemperatures of about 220° F. and of sufficient toughness to beresistant to cutting by serrated polystyrene flatware; said sheet beingcapable of forming a micronodular surface on one side when subjected tovacuum forming.
 49. The sheet of claim 48 having a basis weight of about200-950 lbs. per 3000 square foot ream.
 50. The sheet of claim 48wherein the mica flake aspect ratio is about 30 to 300 at a particlesize of about 50 to about 500 microns.
 51. A microwaveable, food contactcompatible, disposable, rigid and strong, extruded and matted on oneside, sheet consisting essentially of an admixture of a polyolefinselected from the group consisting of polypropylene, polypropylenepolyethylene copolymer or blend, and mixtures of these, mica, a couplingagent for promoting adherence between the polyolefin and mica, andpigment thermoformed by application of vacuum into the shape of acontainer; said sheet exhibiting (a) at least one matted surface, and(b) a softening point of no less than about 250° F.; said sheet beingdimensionally stable and resistant to grease, sugar, and water attemperatures of about 220° F. and of sufficient toughness to beresistant to cutting by serrated polystyrene flatware; said sheet beingcapable of forming a micronodular surface on one side when subjected tovacuum forming.
 52. The sheet of claim or claim 51 wherein the micaflake aspect ratio is about 80 to 120 at a particle size of about 50 to500 microns.
 53. A food contact article comprising polypropylene andmica filler and having a micronodular food contact surface, wherein theaspect ratio of the mica is about 30 to 300 at a particle size of about50 to 500 microns, and wherein the mica is present in an amount from 19to 59 weight percent.
 54. The food contact article of claim 53 whereinsaid micronodular food contact surface exhibits a surface gloss value ofless than about 35 at 75 degrees and a roughness value of at least about12 microns.
 55. A microwaveable, food contact compatible, disposable,rigid and strong container comprising an extruded sheet consistingessentially of an admixture of a polyolefin selected from the groupconsisting of polypropylene, polypropylene polyethylene copolymer orblend, mica having an aspect ratio of about 30 to 300 and a particlesize of about 50 to 500 microns, and pigment thermoformed by applicationof vacuum into the shape of a container; said container furtherexhibiting:(a) a micronodular surface on at least one side of thecontainer surface; and (b) a melting point of no less than about 250°F.;said container being dimensionally stable and resistant to grease,sugar, and water at temperatures up to about 220° F. and of sufficienttoughness to be resistant to cutting by serrated polystyrene flatware,wherein the mica content of the container is about 7 to 59 weightpercent.
 56. A microwaveable, food contact compatible, disposable, rigidand strong container comprising an extruded sheet consisting essentiallyof an admixture of a polyolefin selected from the group consisting ofpolypropylene, polypropylene polyethylene copolymer or blend, and micahaving an aspect ratio of about 30 to 300 and a particle size of about50 to 500 microns, thermoformed by application of vacuum into the shapeof a container; said container further exhibiting:(a) a micronodularsurface on at least one side; (b) a melting point of no less than about250° F.; and (c) a basis weight of at least 130 lbs. per 3000 squarefoot ream;said container being dimensionally stable and resistant togrease, sugar, and water at temperatures up to about 220° F. and ofsufficient toughness to be resistant to cutting by serrated polystyreneflatware, wherein the mica content of the container is about 7 to 59weight percent.
 57. A microwaveable, food contact compatible,disposable, rigid and strong bowl comprising an extruded sheetconsisting essentially of an admixture of a polyolefin selected from thegroup consisting of polypropylene, polypropylene polyethylene copolymeror blend, mica having an aspect ratio of about 30 to 300 and a particlesize of about 50 to 500 microns, and pigment formed or thermoformed intothe shape of a bowl; said bowl exhibiting:(a) a micronodular surface onat least one side; and (b) a melting point of no less than about 250°F.;said bowl being dimensionally stable and resistant to grease, sugar,and water at temperatures up to about 220° F. and of sufficienttoughness to be resistant to cutting by serrated polystyrene flatware,wherein the mica content of the container is about 7 to 59 weightpercent.
 58. A microwaveable, food contact compatible, disposable, rigidand strong plate comprising an extruded sheet consisting essentially ofan admixture of a polyolefin selected from the group consisting ofpolypropylene, polypropylene polyethylene copolymer or blend, micahaving an aspect ratio of about 30 to 300 and a particle size of about50 to 500 microns, and pigment, formed or thermoformed by application ofvacuum into the shape of a plate; said plate exhibiting:(a) amicronodular surface on at least one side; (b) a melting point of noless than about 250° F.; and (c) thickness uniformity characterized by athickness coefficient variation of less than five percent; said platebeing dimensionally stable and resistant to grease, sugar, and water attemperatures up to about 220° F. and of sufficient toughness to beresistant to cutting by serrated polystyrene flatware, wherein the micacontent of the container is about 7 to 59 weight percent.
 59. Amicrowaveable, food contact compatible, disposable, rigid and strong lidcomprising an extruded sheet consisting essentially of an admixture of apolyolefin selected from the group consisting of polypropylene,polypropylene polyethylene copolymer or blend, and mica having an aspectratio of about 30 to 300 and a particle size of about 50 to 500 microns,and pigment, formed or thermoformed by application of vacuum into theshape of a lid; said lid exhibiting:(a) a micronodular surface on atleast one side; and (b) a melting point of no less than about 250°F.;said lid being dimensionally stable and resistant to grease, sugar,and water at temperatures up to about 220° F., wherein the mica contentof the container is about 7 to 59 weight percent.
 60. An extruded sheetwhen thermoformed into a microwaveable, food contact compatible,disposable, rigid and strong container, said sheet consistingessentially of an admixture of a polyolefin selected from the groupconsisting of polypropylene, polypropylene polyethylene copolymer,blend, or mixture, mica having an aspect ratio of about 30 to 300 and aparticle size of about 50 to 500 microns, and pigment, said sheetthermoformed into a container exhibiting a softening point of no lessthan about 250° F., being dimensionally stable and resistant to grease,sugar, and water at temperatures of about 220° F. and of sufficienttoughness to be resistant to cutting by serrated polystyrene flatware,said sheet being capable of forming a micronodular surface on one sidewhen subjected to vacuum forming wherein the mica content of thecontainer of the sheet is about 7 to 59 weight percent.
 61. Amicrowaveable, food contact compatible, disposable, rigid and strongplate comprising an extruded sheet consisting essentially of anadmixture of a polyolefin selected from the group consisting ofpolypropylene, polypropylene polyethylene copolymer or blend, and micahaving an aspect ratio of about 30 to 300 and a particle size of about50 to 500 microns, formed or thermoformed by application of vacuum intothe shape of a plate; said plate comprising about 7 to 59 percent byweight mica and exhibiting:(a) a melting point of no less than about250° F.; and (b) thickness uniformity characterized by a thicknesscoefficient variation of less than five percent; said plate beingdimensionally stable and resistant to grease, sugar, and water attemperatures up to about 220° F. and of sufficient toughness to beresistant to cutting by serrated polystyrene flatware.
 62. Amicrowaveable, food contact compatible, disposable, rigid and strongcontainer comprising an extruded sheet consisting essentially of anadmixture of a polyolefin selected from the group consisting of apropylene-ethylene copolymer or blend, mica wherein the aspect ratio ofthe mica is about 30 to 300 at a particle size of about 50 to 500microns, and pigment thermoformed by application of vacuum into theshape of a container; said container further exhibiting:(a) amicronodular surface on at least one side of the container surface; and(b) a melting point of no less than about 250° F.;said container beingdimensionally stable and resistant to grease, sugar, and water attemperatures up to about 220° F. and of sufficient toughness to beresistant to cutting by serrated polystyrene flatware, wherein theethylene moiety of the propylene-ethylene copolymer or blend comprisesless than ten mole percent of the total copolymer.
 63. A microwaveable,food contact compatible, disposable, rigid and strong containercomprising an extruded sheet consisting essentially of an admixture of apropylene-ethylene copolymer or blend, mica, and pigment, formed orthermoformed into the shape of a container; said container furtherexhibiting:(a) a basis weight of at least 130 pounds per 3000 squarefoot ream; and (b) a melting point of no less than about 250° F.;saidcontainer being dimensionally stable and resistant to grease, sugar, andwater at temperatures up to about 220° F. and of sufficient toughness tobe resistant to cutting by serrated polystyrene flatware, wherein theethylene moiety of the polypropylene or polypropylene polyethylenecopolymer or blend comprises less than ten mole percent of the totalcopolymer.
 64. A microwaveable, food contact compatible, disposable,rigid and strong plate comprising an extruded sheet consistingessentially of an admixture of a polypropylene or propylene-ethylenecopolymer or blend, mica, and pigment, formed, thermoformed, orthermoformed by application of vacuum into the shape of a plate; saidplate exhibiting:(a) a micronodular surface on at least one side of thecontainer surface; (b) a melting point of no less than about 250° F.;and (c) thickness uniformity characterized by a thickness coefficientvariation of less than five percent; said plate being dimensionallystable and resistant to grease, sugar, and water at temperatures up toat least 220° F. and of sufficient toughness to be resistant to cuttingby serrated polystyrene flatware, wherein the ethylene moiety of thepolypropylene or propylene-ethylene copolymer or blend comprises lessthan ten mole percent of the total copolymer.
 65. A microwaveable, foodcontact compatible, disposable, rigid and strong container comprising anextruded sheet consisting essentially of an admixture of a polypropyleneor propylene-ethylene copolymer or blend, mica, a coupling agent forpromoting adherence between the polypropylene or propylene ethylenecopolymer or blend and mica, and pigment, formed, thermoformed, orthermoformed by application of vacuum, into the shape of a container;said container exhibiting:(a) a micronodular surface on at least oneside; and (b) a melting point of no less than about 250° F.;saidcontainer being dimensionally stable and resistant to grease, sugar, andwater at temperatures up to at least 220° F. and of sufficient toughnessto be resistant to cutting by serrated polystyrene flatware, wherein theethylene moiety of the polypropylene or propylene-ethylene copolymer orblend comprises less than ten mole percent of the total copolymer, thecontainer including a base portion and a lid portion comprising: I (a) abottom;(b) an upwardly extending peripheral wall joined to said bottom,said upwardly extending peripheral wall having an inwardly taperingfrusto-conical base seal area formed therein; and (c) a downwardly andoutwardly extending brim joined to said upwardly extending peripheralwall, said brim halving an undercut secondary seal ridge formed therein;and a unitary lid comprising: II (a) a top joined to;(b) a downwardlyextending peripheral wall to; (c) an upwardly extending wall having afrusto-conical lid seal area formed therein, said frusto-conical liddeal area being mateable with the frusto-conical base seal area; (d) adownwardly extending wall having a secondary seal furrow mateable withsaid secondary seal ridge; and (e) resilient lid realignment meanslocated between said secondary seal furrow and said frusto-conical lidseal area for simultaneously urging said frusto-conical base seal areainto close engagement with said frusto-conical lid seal area whileurging said secondary seal ridge into engagement with said secondaryseal furrow.
 66. A microwaveable, food contact compatible, disposable,rigid and strong extruded sheet consisting essentially of apolypropylene ethylene copolymer or blend, mica, and pigmentthermoformed by application of vacuum into the shape of a container,wherein the ethylene content of the polypropylene ethylene copolymer orblend is not more than ten mole percent; said sheet exhibiting asoftening point of no less than about 250° F.; said sheet beingdimensionally stable and resistant to grease, sugar, and water attemperatures of about 220° F. and of sufficient toughness to beresistant to cutting by serrated polystyrene flatware; said sheet beingcapable of forming a micronodular surface on one side when subjected tovacuum forming.
 67. A microwaveable, food contact compatible,disposable, rigid and strong, extruded and matted on one side, sheetconsisting essentially of an admixture of a polypropylene ethylenecopolymer or blend, mica, and pigment thermoformed by application ofvacuum into the shape of a container, wherein the polyethylene contentof the polypropylene ethylene copolymer or blend does not exceed aboutten mole percent; said sheet exhibiting (a) at least one matted surface,and (b) a softening point of no less than about 250° F.; said sheetbeing dimensionally stable and resistant to grease, sugar, and water attemperatures of about 220° F. and of sufficient toughness to beresistant to cutting by serrated polystyrene flatware; said sheet beingcapable of forming a micronodular surface on one side when subjected tovacuum forming.
 68. A microwaveable, food contact compatible,disposable, rigid and strong, mica-filled polyolefin container whereinthe polyolefin is selected from the group consisting of polypropyleneand polypropylene polyethylene copolymer or blend, and a mixture ofthese, said container being prepared according to a methodcomprising:(a) forming an extrudable admixture of the polyolefin resinand mica; (b) extruding said extrudable admixture of the polyolefinresin and mica at elevated temperature (c) passing the resultingextruded admixture of the polyolefin resin and mica through a multipleroll stack, at least one roll of said stack having a matte finish; (d)passing said extruded admixture of the polyolefin resin and mica atleast partially around said roll having a matte finish; (e) controllingthe speed of said extrusion process, the size, temperature andconfiguration of said roll stack such that the surface of said extrudedadmixture of the polyolefin resin and mica not in contact with saidmatte roll has a coarse-grained structure; (f) thermoforming saidextruded admixture of the polyolefin, resin, and mica; and (g)recovering a container having a micronodular surface and a rough surfaceand exhibiting a melting point of no less than 250° F., said containerbeing dimensionally stable and resistant to grease, sugar, and water attemperatures up to about 220° F. and having sufficient toughness to beresistant to cutting by serrated flatware.
 69. A microwaveable, foodcontact compatible, disposable, rigid and strong, mica-filled polyolefinplate wherein the polyolefin is selected from the group consisting ofpolypropylene and polypropylene polyethylene copolymer or blend, and amixture of these, said plate being prepared according to a methodcomprising:(a) forming an extrudable admixture of the polyolefin resinand mica; (b) extruding said extrudable admixture of the polyolefinresin and mica at elevated temperature (c) passing the resultingextruded admixture of the polyolefin resin and mica through a multipleroll stack, at least one roll of said stack having a matte finish; (d)passing said extruded admixture of the polyolefin resin and mica atleast partially around said roll having a matte finish; (e) controllingthe speed of said extrusion process, the size, temperature andconfiguration of said roll stack such that the surface of said extrudedadmixture of the polyolefin resin and mica not in contact with saidmatte roll has a coarse-grained structure; (f) thermoforming saidextruded admixture of the polyolefin, resin, and mica; and (g)recovering a plate having a micronodular surface and a rough surface andexhibiting a melting point of no less then 250° F., said container beingdimensionally stable and resistant to grease, sugar, and water attemperatures up to about 220° F. and having sufficient toughness to beresistant to cutting by serrated flatware.
 70. A microwaveable, foodcontact compatible, disposable, rigid and strong, mica-filled polyolefincup wherein the polyolefin is selected from the group consisting ofpolypropylene and polypropylene polyethylene copolymer or blend, and amixture of these, said cup being prepared according to a methodcomprising:(a) forming an extrudable admixture of the polyolefin resinand mica; (b) extruding said extrudable, admixture of the polyolefinresin and mica at elevated temperature (c) passing the resultingextruded admixture of the polyolefin resin and mica through a multipleroll stack, at least one roll of said stack having a matte finish; (d)passing said extruded admixture of the polyolefin resin and mica atleast partially around said roll having a matte finish; (e) controllingthe speed of said extrusion process, the size, temperature andconfiguration of said roll stack such that the surface of said extrudedadmixture of the polyolefin resin and mica not in contact with saidmatte roll has a coarse-grained structure; (f) thermoforming saidextruded admixture of the polyolefin, resin, and mica; and (g)recovering a cup having p micronodular surface and a rough surface andexhibiting a melting point of no less than 250° F., said container beingdimensionally stable and resistant to grease, sugar, and water attemperatures up to about 220° F. and having sufficient toughness to beresistant to cutting by serrated flatware.
 71. A microwaveable, foodcontact compatible, disposable rigid and strong, mica-filled polyolefinbowl wherein the polyolefin is selected from the group consisting ofpolypropylene and polypropylene polyethylene copolymer or blend, and amixture of these, said bowl being prepared according to a methodcomprising:(a) forming an extrudable admixture of the polyolefin resinand mica: (b) extruding said extrudable admixture of the polyolefinresin and mica at elevated temperature (c) passing the resultingextruded admixture of the polyolefin resin and mica through a multipleroll stack, at least ore roll of said stack having a matte finish; (d)passing said extruded admixture of the polyolefin resin and mica atleast partially around said roll having a matte finish; (e) controllingthe speed of said extrusion process, the size, temperature andconfiguration of said roll stack such that the surface of said extrudedadmixture of the polyolefin resin and mica not in contact with saidmatte roll has a coarse-rained structure; (f) thermoforming saidextruded admixture of the polyolefin, resin, and mica; and (g)recovering a bowl having a micronodular surface and a rough surface andexhibiting a melting point of no less than 250° F., said container beingdimensionally stable and resistant to grease, sugar, and water attemperatures up to about 220° F. and having sufficient toughness to beresistant to cutting by serrated flatware.
 72. A microwaveable, foodcontact compatible, disposable, rigid and strong, mica-filled polyolefintray wherein the polyolefin is selected from the group consisting ofpolypropylene and polypropylene polyethylene copolymer or blend, and amixture of these, said tray being prepared according to a methodcomprising:(a) forming an extrudable admixture of the polyolefin resinand mica; (b) extruding said extrudable admixture of the polyolefinresin and mica at elevated temperature (c) passing the resultingextruded admixture of the polyolefin resin and mica through a multipleroll stack, at least one roll of said stack having a matte finish; (d)passing said extruded admixture of the polyolefin resin and mica atleast partially around said roll having a matte finish; (e) controllingthe speed of said extrusion process, the size, temperature andconfiguration of said roll stack such that the surface of said extrudedadmixture of the polyolefin resin and mica not in contact with saidmatte roll has a coarse-rained structure; (f) thermoforming saidextruded admixture of the polyolefin, resin, and mica; and (g)recovering a tray having a micronodular surface and a rough surface andexhibiting a melting point of no less than 250° F., said container beingdimensionally stable and resistant to grease, sugar, and water attemperatures up to about 220° F. and having sufficient toughness to beresistant to cutting by serrated flatware.
 73. A microwaveable, foodcontact compatible, disposable, rigid and strong, mica-filled polyolefinbucket wherein the polyolefin is selected from the group consisting ofpolypropylene and polypropylene polyethylene copolymer or blend, and amixture of these, said bucket being prepared according to a methodcomprising:(a) forming an extrudable admixture of the polyolefin resinand mica; (b) extruding said extrudable admixture of the polyolefinresin and mica at elevated temperature (c) passing the resultingextruded admixture of the polyolefin resin and mica through a multipleroll stack, at least one roll of said stack having a matte finish; (d)passing said extruded admixture of the polyolefin resin and mica atleast partially around said roll having a matte finish; (e) controllingthe speed of said extrusion process, the size, temperature andconfiguration of said roll stack such that the surface of said extrudedadmixture of the polyolefin resin and mica not in contact with saidmatte roll has a coarse-rained structure; (f) thermoforming saidextruded admixture of the polyolefin, resin, and mica; and (g)recovering a bucket having a micronodular surface and a rough surfaceand exhibiting a melting point of no less than 250° F., said containerbeing dimensionally stable and resistant to grease, sugar, and water attemperatures up to about 220° F. and having sufficient toughness to beresistant to cutting by serrated flatware.
 74. A microwaveable, foodcontact compatible, disposable, rigid and strong, mica-filled polyolefinsouffle dish wherein the polyolefin is selected from the groupconsisting of polypropylene and polypropylene polyethylene copolymer orblend, and a mixture of these, said souffle dish being preparedaccording to a method comprising:(a) forming an extrudable admixture ofthe polyolefin resin and mica; (b) extruding said extrudable admixtureof the polyolefin resin and mica at elevated temperature (c) passing theresulting extruded admixture of the polyolefin resin and mica through amultiple roll stack, at least one roll of said stack having a mattefinish; (d) passing said extruded admixture of the polyolefin resin andmica at least partially around said roll having a matte finish; (e)controlling the speed of said extrusion process, the size, temperatureand configuration of said roll stack such that the surface of saidextruded admixture of the polyolefin resin and mica not in contact withsaid matte roll has a coarse-grained structure; (f) thermoforming saidextruded admixture of the polyolefin, resin, and mica; and (g)recovering a souffle dish having a micronodular surface and a roughsurface and exhibiting a melting point of no less than 250° F., saidcontainer being dimensionally stable and resistant to grease, sugar, andwater at temperatures up to about 220° F. and having sufficienttoughness to be resistant to cutting by serrated flatware.
 75. Amica-filled polyolefin extruded sheet wherein the polyolefin is selectedfrom the group consisting of polypropylene and polypropylenepolyethylene copolymer or blend, and a mixture of these, said sheetbeing prepared according to a method comprising:(a) forming anextrudable admixture of the polyolefin resin and mica; (b) extrudingsaid extrudable admixture of the polyolefin resin and mica at elevatedtemperature; (c) passing the resulting extruded admixture of thepolyolefin resin and mica through a multiple roll stack, at least oneroll of said stack having a matte finish; (d) passing said extrudedadmixture of the polyolefin resin and mica at least partially aroundsaid roll having a matte finish; (e) controlling the speed of saidextrusion process, the size temperature and configuration of said rollstack such that the surface of said extruded admixture of the polyolefinresin and mica in contact with said matte roll has a matted structure;and (f) recovering a sheet comprising polyolefin and mica, said sheethaving a matted surface and a rough surface.
 76. A mica-filledpolypropylene or polypropylene polyethylene copolymer or blend extrudedsheet prepared according to a method comprising:(a) forming anextrudable admixture of polypropylene or polypropylene polyethylenecopolymer or blend resin land mica; (b) extruding said extrudableadmixture of polypropylene or polypropylene polyethylene copolymer orblend resin and mica at elevated temperature; (c) passing the resultingextruded admixture of polypropylene or polypropylene polyethylenecopolymer or blend resin and mica through a multiple roll stack, atleast one roll of said stack having a matte finish; (d) passing saidextruded admixture of polypropylene or polypropylene polyethylenecopolymer or blend resin and mica at least partially around said rollhaving a matte finish; and (e) controlling the speed of said extrusionprocess, the size, temperature and configuration of said roll stack suchthat the surface of said extruded admixture of polypropylene orpolypropylene polyethylene copolymer or blend resin and mica in contactwith said matte roll has a matted structure; and (f) recovering a sheetcomprising a polypropylene or polypropylene polyethylene copolymer orblend and mica, said sheet having a matted surface and a rough surface.